PRACTICAL 

-— K-* 


MICROSCOPY 


A  COURSE  OF  NORMAL  HISTOLOGY 


FOR 


Students  and  Practitioners  of  Medicine 


MAURICE   N.  MILLER,  M.D., 

\\ 

Director  of  the  Department  of  Normal  Histology  in  the  Loomis  Laboratory,  University  of  the 

City  of  New  York 


ILLUSTRATED  WITH  ONE  HUNDRED  AND  TWENTY-SIX    PHOTOQRAPHICAL 
REPRODUCTIONS  OF  THE  AUTHOR'S  PEN  DRAWINGS 


NEW   YORK 

WILLIAM    WOOD    &    COMPANY 
18.91 


COPYRIGHT  BY 
WILLIAM  WOOD  &  COMPANY 

1887 


^^e  Carton  (press 

171,  173  Macdougal  Street,  New  York 


ALFEED   L.  LOOMIS,  M.D.,  LL.D., 

PROFESSOR    OF    PATHOLOGY     AND     PRACTICE     OF    MEDICINE 

MEDICAL     DEPARTMENT     UNIVERSITY     OF     THE 

CITY    OF    NEW    YORK,    ETC.,    ETC., 


is 


BY    THE    AUTHOR. 


PREFACE. 


THIS  volume  has  been  prepared  with  a  view  of  aiding  the 
instructors  and  students  of  the  laboratory  classes  which  are 
under  my  direction. 

It  is  also  presented  with  the  hope  that  it  may  be  useful  to 
other  instructors. 

Again,  students  often  wish  to  continue  microscopical  work 
during  the  interim  of  college  attendance;  to  such,  it  is  my  be- 
lief, these  pages  will  have  some  value. 

Still  again,  very  many  practitioners,  not  having  had,  dur- 
ing pupilage,  advantages  equal  to  those  provided  by  the 
modern  laboratory  equipment,  wish  to  acquire  more  knowl- 
edge of  microscopy,  for  its  value  in  practical  medicine.  To 
such  workers,  also,  I  desire  to  be  useful. 

So  much  technique  has  been  introduced  as  has  been  found 
to  be  of  absolute  necessity,  and  no  more.  The  processes  for 
the  preparation  and  exhibition  of  tissues  are  generally  simple 
and  always  practicable. 

In  the  description  of  organs,  I  assume  the  student  has  a 
fair  knowledge  of  gross  anatomy,  but  knows  nothing  of  his- 
tology. The  scheme  or  plan  of  the  structure  is  first  described 
— using  diagrams  where  requisite  to  clearness — after  which 
the  mode  of  preparing  the  sections  indicated,  and,  under 
practical  demonstration,  every  histological  detail  tabulated  in 
proper  order.  The  drawings  will,  I  believe,  aid  in  the  recog- 
nition of  such  elements  in  the  field  of  the  microscope. 

The  illustrations  are  exact  reproductions,  by  photography, 
of  my  own  pen-pictures;  and  distinction  must  always  be  made 
between  the  drawings  which  are  schematic — used  to  empha- 


vi  PREFACE. 

size  the  plan  of  structures — and  those  drawn  from  the  tissue 
as  seen  in  the  microscope. 

Our  literature  abounds  in  excellent  works  for  the  advanced 
student,  and  this  volume  is  designed  to  pave  the  way  for  their 
appreciation. 

I  desire  to  record  ni3r  hi^h  appreciation  of  the  aid  of  Drs. 
Charles  T.  Jewett,  Egbert  Le  Fevre,  E.  Eliot  Harris,  Milton 
Turnure,  H.  Pereira  Mendes,  J.  Gorman,  A.  M.  Lesser,  J.  Alex- 
ander Moore,  Robert  Roberts,  Esq.,  Warden,  and  Mr.  John 
Burns,  Clerk  of  Charity  Hospital,  in  facilitating  my  access  to 
valuable  tissue  for  the  illustrations  and  for  my  own  studies. 

M}'  thanks  are  due  my  First  Assistant,  Dr.  F.  T.  Reyling, 
for  his  indefatigable  efforts  in  furthering  the  work;  and  to 
Mr.  A.  J.  Drummond,  for  photographical  favors. 

MAURICE  N.  MILLER. 
NEW  YORK,  June  1st,  1887. 


CONTENTS. 


Title-page,  Dedication,  List  of  Illustrations,  and  Table  of  Con- 
tents,      .  .  i.  to  xv. 


PAET  FIBST. 
TECHNOLOGY. 

THE  LABORATORY  MICROSCOPE. 

Description  of  the  Stand,    .......  1 

Lenses,       .........  3 

General  Adjustment,           .......  4 

Adjustment  for  Illumination,  ......  4 

Adjustment  for  Focus,        .  .  .  .  .  .5 

Method  in  Observation,             .            .            .            .            .            .  6 

Conservation  of  the  Eyesight,       ......  7 

Magnifying  Power,         .......  7 

Measurement  of  Objects,    ....  8 

Sketching  from  the  Instrument,         .....  9 

PREPARATION  OF  TISSUES  FOR  MICROSCOPICAL 

PURPOSES. 
Tissue  Teasing,         ........        9 

Section  Cutting, ........  9 

Free-hand  Section  Cutting,  ......      10 

Cutting  with  the  Stirling  Microtome,  .  .  .  .  12 

Cutting  with  Schrauer's  Microtome,       .  .  .  .12 

Cutting  with  the  Author's  Microtome,          ....  14 

Sharpening  Knives — Honing  and  Stropping,  .  .  .  .16 

Paraffin  Soldering,         ...  .  18 

Tissue  Hardening,    ......  .20 

Rapid  Hardening  with  Alcohol,          ...  21 

Hardening  with  Miiller's  Fluid,   . 

Hardening  with  Chromic  Acid,  .... 

Decalcifying  and  Dissociating,     ..... 

Imbedding  and  Infiltrating  with  Bayberry  Wax,  . 

Imbedding  and  Infiltrating  with  Celloidin,      .  .  .  .2* 


CONTENTS. 


Freezing.    .... 

Staining  Methods  in  General,       .  .  .  • 

S  raining  with  Htenmtoxylin,    .  ... 

Staining  with  Hamia.  and  Eosin, 

Staining  with  Carmine, 

Staining  with  Carmine  and  Picric  Acid,  .  ~  ' 

Staining  with  Silver  Nitrate,  . 

Cleaning  Slides  and  Cover-glasses, 

Mounting  Methods, 

Labelling  Slides,       . 

Care  of  the  Microscope,  ......  34 


PART  SECOND. 
STRUCTURAL  ELEMENTS. 

PRELIMINARY  STUDY. 

•  •  -' 

Form  of  Objects,      ....  .  .      35 

Movements  of  Objects,  .  ... 

Extraneous  Substances,     ......•« 

CELLS. 

Cell  Distribution,           ......  40 

Variation  in  Cell  Forms,    .....  .40 

Flat  Cells,  ....  . 

Squamous,  Stratified,  and  Transitional  Epithelium,  .           .      41 

Pavement  Epithelium,  ...  • 

Columnar  Epithelium, 

Ciliated  Columnar  Epithelium,          .           .        ^  .           .  45 

Spherical  Cells .47 

Red  Blood-Corpuscles,              .....  47 

Blodd  Plates .48 

Colorless  Blood-Corpuscles,      ....  49 

Polyhedral  Cells, .49 

Stellate  Cells, 50 

Polar  Cells, .           .      50 

CONNECTIVE  (FIBROUS)  TISSUES. 

White  Fibrous  Tissue,  ...  .  .  51 

Yellow  Elastic  Tissue  52 

Adipose  Tissue,  ...  ....  54 

CARTILAGE. 

Hyaline  Cartilage,   ........      55 

Elastic  Cartilage,          ....  56 

Fibro-elastic  Cartilage,       .  ...      57 


CONTENTS.  ix 

PAGE 
BONE,        ...  58 

SPECIAL  CONNECTIVE   TISSUES. 

Adenoid  Tissue,        .......  .61 

Neuroglia,  ........  61 

Embryonic  Tissue,   ........      62 

MUSCULAR   TISSUE. 

Non-striated  Muscle,  .....  .62 

Striated  Muscle,  .......  63 

Cardiac  Muscle,        .  .  .  .  ...  .65 

BLOOD-VESSELS. 

Arteries,    ....  ....  66 

Capillaries,     .........      67 

Veins,         ......  67 


PAET  THIED. 
ORGANS. 

THE   SKIN. 

Layers  or  Strata,  .  .  .  .  .  .  .  68 

Hairs,  .........  71 

Sudoriferous  Glands,     .......  72 

Sebaceous  Glands,   ...  ....  74 

THE  TEETH. 

The  Pulp,  ........  78 

Dentine,         .........  78 

Enamel,     .....  ...  79 

Crusta  Petrosa,         .  .  .  .'.,•".  .  .  .80 

Practical  Demonstration,         .  ...  89 D 

THE  STOMACH  AND   INTESTINES. 

General  Histology,  ........  83 

The  Stomach,      ........  84 

Practical  Demonstration,  .....  .87 

Small  Intestine,  ......  88 

Practical  Demonstration,  .......  92 

THE  LUNG. 

Bronchial  Tubes,  ...  94 

Coats,  ...  ...  95 

Practical  Demonstration,         .  .  97 

Pulmonary  Blood-vessels,  .  .  .  .99 


X  CONTENTS. 

PAGE 

The  Pleura,         .                                                         .           .'.  .          100 
1 'uli nonary  Alveoli,             .                                               ...     101 

Practical  Demonstration,  Lung  of  Pig,        .  .          103 

Practical  Demonstration,  Human  Lung,          .                       ,  .     105 

THE  LIVER. 

General  Scheme,            .           .           .          , .                       .  .          106 

The  Portal  Canals,                                                                       .  •     108 

The  Lobular  Parenchyma,      .           .                                  .  109 

Practical  Demonstration,  Liver  of  Pig,  .  .110 

Practical  Demonstration,  Human  Liver,    .           .           .  .          113 

Practical  Demonstration,  The  Portal  Canals,  .  .114 

Practical  Demonstration,  The  Lobular  Parenchyma,      .  116 

Practical  Demonstration,  Origin  of  Bile  Ducts,          .           .  .     118- 

THE  KIDNEY. 

General  Description,     .....  .          120 

The  Tubuli  Uriniferi,          ....  .122 

Blood-vessels,      .           .           .           .           .           .           •'.  .          124 

Practical  Demonstration,  with  Low  Power,      .           »          \-  .    128 

Practical  Demonstration,  The  Cortical  Portion,    .            .  .           130 

Practical  Demonstration,  Medullary  Portion,  .           .           .  .    13£ 

THE  GENITO-URINARY  TRACT.  URETER,  BLADDER, 

UTERUS,  VAGINA,  ETC. 

General  Histology,        .           .           .           .           #  .•        .  .          135 

Practical  Demonstration,  Uterus  and  Vagina,             .           .  .     136 

Practical  Demonstration,  Pelvis  of  the  Kidney,    .           .  .          140 

Practical  Demonstration,  The  Urinary  Bladder,        .           .  .141 

Practical  Demonstration,  Urinary  Deposits,        . .           ,  .          14& 

THE  OVARY. 

Practical  Demonstration,  Adult  Human  Ovary,         .           .  .     144 

DEVELOPMENT  OF  THE  OVUM. 

Practical  Demonstration,  Foetal  Ovary,     ....  147 

THE  SUPRA-RENAL  CAPSULE,    .  .  150 

Practical  Demonstration,        ......  151 

SALIVARY  GLANDS.  PANCREAS.  PLAN  OF  GLAND 
STRUCTURE. 

Typical  Glandular  Histology,            ....  153 

Tubular  Glands,       .......  153 

Coiled  Tubular  Glands,           .....  154 

Branched  Tubular  Glands,   .  .  .... 

Acinous  Glands,             ......  155 

The  Parotid  Gland, 


CONTENTS.  xi 

PAGE 

Submaxillary  Gland,    ......       £}%&*       15$ 

Practical  Demonstration,   Parotid  Gland,  Submaxillary  Gland, 

Pancreas,  ........     157 

THE  LYMPHATIC   SYSTEM. 

General  Description,     .......          161 

Lymph  Channels,     .  .  .  .  .  .  .  .162 

•Practical  Demonstration,  Lymph  .Channels  of  Central  Tendon  of 

the  Diaphragm,       .......  163 

Lymphatic  Nodes  or  Glands,        ......     167 

Practical  Demonstration,  Mesenteric  Lymph  Node,        .  169 

THE  SPLEEN. 

Scheme  of  Organ,     ........     173 

Practical  Demonstration,         ....  174 

THE  THYMUS  BODY. 

General  Description,  .  .  .  .  .  .  .177 

Practical  Demonstration,         ......  178 

THE  NERVOUS  SYSTEM. 

Structural  Elements,           .            .            .            .            .            .    '  .     180 

Nerve  Fibres,      ........  180 

Nerve  Cells,   ......  .     181 

Connective  Tissue  of  Nerve  Trunks,            .            ...  182 

Neuroglia,      .            .           .            .           .'          .           .           .  .183 

THE  SPINAL  CORD. 

General  Description,     .  ....          186 

Practical  Demonstration,  Cervical  Spinal  Cord,         .  .  .187 

THE  BRAIN. 

Membranes,         .  .  .  .  .  .  .          191 

Practical  Demonstration,  Cerebrum,      .  ...     192 

Practical  Demonstration,  Cerebellum,         ....          195 

MISCELLANEOUS  FORMULA,  ETC. 

Dammar  Mounting  Varnish,         ......     197 

Xylol  Balsam,      ........          197 

Varnishes  and  Cements  for  Ringing  Mounts ;  Dammar  Varnish  ; 

Zinc   Cement ;   Aniline  Colors ;    Oil  Colors ;    Black    Varnish ; 

Shellac  Varnish,  .  .  .  .  .  .  .197 

Preservative  Fluid,        .  .  .  .  .  .  .199 

Normal  Salt  Solution,         .  ...  .  .199 

Razor-Strop  Paste,  .  .  .  199 


x  i  i  CONTENTS. 

Silvor  Staining  Solution,   .  . 

OH i lie  Acid  Solution,     . 

Weigert's  Staining  for  Medullated  Nerve  Tissue, 

Bayberry  Infiltrating  Method, 

KaVyokinesis,  . 

Fixing  and  Staining  Corpuscular  Elements  of  Blood, 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1.  Laboratory  Microscope,             .            .            .                       .  '.2 

2.  Course  of  Light  Through  the  Microscope,          ...  3 

3.  Free-hand  Section  Cutting,      ....  .10 

4.  Stirling  Microtome,              ......  12 

5.  Method  of  Imbedding  with  Pith,  Turnip,  etc.,       .            .  .13 

6.  Section  Cutting  with  Stirling  Microtome,           ...  14 

7.  The  Schrauer  Microtome,         .            .           .            .           .  .14 

8.  The  Author's  Laboratory  Microtome1,     .            .            .            .  15 

9.  Method  of  Honing  Razor,          .            .            .            .            .  .17 

10.  Turning  the  Razor  on  the  Hone,  .  .  .  .  .17 

11.  Paraffin  Soldering  Wire,            .            .            .            .            .  .18 

12.  Cementing  Hardened  Tissue  to  Cork,      ...  19 

13.  Needle  for  Handling  Sections,  Covers,  etc.,             .           .  .20 

14.  Diagram  Illustrating  Steps  in  Staining  with  Hsenia.,            .  25 

15.  Diagram  Illustrating  Steps  in  Staining  with  Hsema.  and  Eosin,    26 

16.  Diagram  Illustrating  Steps  in  Staining  with  Borax-Carmine,  .     26 

17.  Section  Lifter,            .......  32 

18.  Appearance  of  Balsam  Mounted  Specimen,             .            .  .33 

19.  Mode  of  Handling  Cover-glass,      .....  32 

20.  Diagram  Showing  Effect  of  Oil  and  Air  Globules,              .  .     36 

21.  Extraneous  Substances — Hairs,  etc.,        ....  37 

22.  Extraneous  Substances — Starch,  etc.,            .            .            .  .38 

23.  Elements  of  a  Typical  Cell,            ......  39 

24.  Structure  of  a  Cell-Nucleus,     .           .            .           .           .  .40 

25.  Squamous  Cells  from  Saliva,          .  .  .  .41 

26.  Pavement  Epithelium,  .           .           .            .           .           .  .42 

27.  Frog's  Mesentery— Silver  Staining,          ....  43 

28.  Columnar  Cells  from  Intestine,            .            .            .            .  .     4c 

29.  Ciliated  Cells  from  Bronchus,        .  .  .  .  .46 

30.  Diagram  Showing  Organs  of  the  Oyster,       .            .            .  .46 
81.  Corpuscular  Elements  of  Human  Blood,             ...  47 

32.  Diagram.     Human  Red-Blood  Corpuscle  in  Profile,        .  .  .48 

33.  Blood  Plaques,           .           .  49 

34.  Glandular  Cells  from  Liver,     .                       .  .50 

35.  Fibrillated  Connective  Tissue,           .            .  52 

36.  Yellow  Elastic  Tissue,        .           .  53 

37.  Transverse  Section  of  Ligamentum  Nuchse,           .            .  .53 


xiv  LIST    OF    I  IJJ-ST  RATIONS. 


38.  Cells  containing  Fat,          .  •  .DO 

39.  Adipose  Tissue  from  Omentuin,  .    • 

40.  Hyaline  Cartilage  from  Bronchus, 

41.  Fibro-Cartilage  from  Intervertebral  Disc,    .  •  57 

42.  Elastic  Cartilage  from  Pinna  of  Ox,       .  57 

43.  Bone—  Showing  Laminated  Structures,      .  .58 

44.  Bone—  Showing  Haversian  Systems, 

45.  Contents  of  Haversian  Canals, 

46.  Contents  of  Bone  Lacuna, 

47.  Bladder  of  Frog—  Showing  Non-Striated  Muscle, 

48.  Diagram—  Illustrating  Structure  of  Striated  Muscular  Fibre, 

49.  Striated  Muscular  Fibre  from  Tongue,-      . 

50.  Cardiac  Muscular  Fibre,    . 

51.  Artery  in  Transverse  Section, 

52.  Blood  Capillaries,    . 

53.  Layers  of  the  Epidermis,  •  69 

54.  Structure  of  the  Derma,     .  70 

55.  Hair  in  Transverse  Section,    .  .  71 

56.  Hair  Follicle, 

57.  Sudoriferous  Gland,      .  •  ^' 

58.  Sebaceous  Gland,     ...  .  73 

59.  Skin  in  Vertical  Section,          ....  .75 

60.  Human  Canine  Tooth  in  Vertical  Section.       .  .  79 

61.  Fang  of  Tooth  in  Transverse  Section, 

62.  Stomach.    Diagram,  83 

63.  Cardiac  Gastric  Glands,  .  .  .  .85 

64.  Pyloric  Gastric  Glands,     .  .  .  86 

65.  Stomach  of  Dog, 

66.  Diagram  Illustrating  Intestinal  Secretion,    -   .  .89 

67.  Diagram  of  Intestinal  Absorption,   .  .  .  .  90 

68.  Small  Intestine  with  Peyer's  Lymphatics,       .  ..-  92 

69.  Bronchial  Tube  Arrangement,  .  .  94 

70.  Bronchial  Tube—  Small,     .  .  .  •  *        «,  96 

71.  Bronchial  Tube  —  Medium,      .  .         ....••.        .  .  .98 

72.  Pulmonary  Lobule  —  Perspective,  .          ,.  .  .  101 

73.  Pulmonary  Lobule  —  Longitudinal  Section,  .  .  .  101 

74.  Pulmonary  Alveolus  —  Capillaries  Filled,          .  .  .  102 

75.  Lung  of  Pig,        ........  103 

76.  Pulmonary  Alveolus  Showing  Lining,  ....  104 

77.  Liver.     Diagram  Illustrating  Plan  of  Structure,  .  .  .  107 

78.  Glandular  Cells  in  Connection  with  Blood-vessels  and  Ducts,  109 

79.  Liver  of  Pig  .....  ....  Ill 

80.  Human  Liver  —  Low  Power,          .  .  .  .  .  114 

81.  Portal  Canal,      ...  .....  115 

82.  Hepatic  Cells—  Detached,  ......  117 

83.  Hepatic  Lobule  in  Transverte  Section,       ....  118 

84.  Bile  Capillaries—  Or-igin  of  Bile  Duct,    ....  119 

85.  Kidney—  Diagram  Illustrating  Plan  of  Structure,  .  .  121 

86.  Kidney  Tubules—  Isolated,  .  123 


LIST   OF   ILLUSTRATIONS.  XV 


FIG.  PAGE 

87.  Blood-vessels — Arrangement  in  Kidney,    ....  125 

88.  Kidney— Low  Power,       ......  128 

89.  Kidney— Cortex  in  Vertical  Section,          .  .  .  .130 

90.  Kidney — Medulla  in  Longitudinal  Section,     .            .            .  132 

91.  Kidney — Medulla  in  Transverse  Section,  ....  133 

92.  Uterus  with  Vaginal  cul-de-sac,            ....  136 

93.  External  Uterine  Os,           .               .....  138 

94.  Vaginal  Epithelium,         .            .            .            .            ...  139 

95.  Epithelium  of  Ureter,  .  .  .  .  .  .140 

96.  Epithelium  of  Urinary  Bladder,            .            .           •            .  142 

97.  Epithelium  from  Urinary  Deposit, .....  143 

98.  Ovary— Adult,        .            .            .            .            .            .            .  145 

99.  Ovary— Foetal,              .                       148 

100.  Suprarenal  Capsule — Low  Power,         ....  151 

101.  Suprarenal  Capsule — High  Power,  .  .  .    152 

102.  Simple  Tubular  Gland,    ......  153 

103.  Coiled  Tubular  Gland, 154 

104.  Branched  Tubular  Gland,  .....  155 

105.  Dilated  Tubular  Gland,         .  .  .  .  .  .156 

106.  Parotid  Gland,        .......          156 

107.  Submaxillary  Gland,  .  .  .  .  .  .157 

108.  Pancreas,      ....  ...          158 

109.  Perivascular  Lymph  Spaces,  .....     162 

110.  Lymphatics    of    Central    Tendon    of    the  Diaphragm — Low 

Power,    ........          165 

111.  Lymphatics  of  Central    Tendon  of    the   Diaphragm — High 

Power,  .....  .     166 

112.  Lymph  Node — Diagrammatic,   ....  168 

113.  Mesenteric  Lymph  Node — Low  Power,      ....     170 

114.  Mesenteric  Lymph  Node — High  Power,  .  .  .  171 

115.  Blood-vessel  Arrangement  in  the  Spleen,  .  .  .     173 

116.  Spleen,          .  .  .  .  .  .  .175 

117.  Thymus  Body,  .......     178 

118.  Nerve  Fibre,  .......          180 

119.  Connective  Tissue  of  Nerve  Trunk,  .  .     182 

120.  Connective  Tissue  of  Brain,        .  .  .183 

121.  Spinal  Cord— Diagram,          ...  .185 

122.  Cervical  Spinal  Cord— Transverse  Section,     ...          188 

123.  Anterior  Cornu  of  Gray  Matter— Cervical  Spinal  Cord,  .    189 

124.  Cerebrum,    ....  ...          193 

125.  Cerebellum — Low  Power,      ......     194 

126.  Cerebellum— High  Power,  .....          195 


PRACTICAL    MICROSCOPY 


PART    FIRST. 


TECHNOLOGY. 


THE   LABORATORY   MICROSCOPE. 

THE  histologist  should  be  provided  with  a  microscope,  in  which 
the  principal  features  of  the  laboratory  instrument,  Fig.  1,  are  em- 
braced. 

The  body  A,  which  carries  the  optical  parts,  is  made  of  two 
pieces  of  brass  tubing,  one  sliding  within  the  other  and  providing 
for  alterations  in  length.  The  objectives,  C,  D,  are  attached  to  the 
body  by  means  of  the  angular  carrier  E.  The  carrier  is  so  pivoted 
that  either  objective  may  be  turned  into  the  optical  axis,  at  will. 
The  eye-piece,  F,  slips  into  the  upper  part  of  the  body,  with  but 
little  friction,  so  that  it  may  be  quickly  and  easily  removed. 

The  coarse  or  quick  adjustment  for  focussing  consists  of  a  rack 
G,  which  is  attached  to  the  body,  and  into  this  gears  a  small  (con- 
cealed) pinion  turned  by  the  milled-head  H. 

The  fine  steel  screw  I,  by  means  of  which  the  more  delicate 
adjustments  for  focussing  are  accomplished,  terminates  below  in  a 
hardened  point,  which  impinges  upon  one  end  of  a  lever  (concealed 
in  the  arm),  the  fulcrum  of  the  same  being  indicated  at  the  point 
J.  The  opposite  end  of  the  lever  is  inserted  in  a  notch  in  the  split 
arm  K.  By  turning  the  milled-head  L,  the  lever  is  moved,  and 
the  optical  body  raised  or  lowered  with  extreme  delicacy. 

The  stage,  upon  which  objects  are  placed  for  examination,  i» 
perforated  at  M,  and  a  rotating  disc — not  indicated  in  the  drawing 
— enables  one  to  alter  the  size  of  the  opening  at  will.  Below  the 


PRACTICAL    MICROSCOPY. 


stage  an  arm  may  be  seen  which  carries  a  fork  supporting  the 
mirror  N. 

The  whole  is  supported  on  a  short,  stout  pillar  rising  from  the 
foot  0. 


FIG.  1.— THE  LABORATORY  MICROSCOPE. 

This  instrument  was  designed  and  constructed  for  the  laboratories  of  the  New  York  Uni- 
versity Medical  College.  It  is  strongly  built;  the  mechanism  is  simple;  and  the  height— 1(% 
inches— not  too  great  for  use  in  the  vertical  position. 


LENSES   OF   THE    MICROSCOPE. 

Fig.  2  shows  the  arrangement  of  lenses,  including  a  high-power 
objective  of  the  Wenham  construction. 

The  objective  A  is  provided  with  one  simple  and  two  compound 
lenses.  The  lens  B,  nearest  the  object,  and  the  one  upon  which 
the  magnifying  power  mainly  depends,  is  an  hemisphere  of  crown 
glass.  Such  a  figured  glass  possesses  both  chromatic  and  spherical 
aberration  in  high  degree.  These  faults  are  corrected  by  the  com- 
pound flint  and  crown  lenses,  C  and  D,  placed  above  the  hemi- 
spherical glass. 

The  eye-piece  consists  of  two  crown-glass,  plano-convex  lenses, 


LENSES    OF    THE    MICROSCOPE. 


with  their  plane  surface  upward.  The  lower,  E,  is  known  as  the 
field-lens,  the  upper,  F,  as  the  eye-lens.  Eye-pieces  add  very  mate- 
rially to  the  magnifying  power  of  the  instrument,  and  are  con- 
structed of  various  strengths  depending  upon  the  curvature  of  the 


FIG.  2.— DIAGRAM  SHOWING  THE  RELATION  OF  THE  OBJECTIVE  TO  THE  EYE-PIECE. 


lenses.     They  are  named  according  to  power  A,  B,  0,  etc.     The 
medium,  B,  is  more  commonly  employed. 

The  microscope  previously  described  stands,  with  the  draw-tube 
in  place,  about  ten  and  one-half  inches  high;  and  represents  the 
instruments  used  in  the  New  York  University  Laboratory  of  Biol- 


PRACTICAL    MICROSCOPY. 

ogy  and  Pathology.  They  were  constructed  by  Schrauer,  of  this 
city,  costing  about  fifty-five  dollars  each.  They  are  provided  with 
a  single  eye-piece,  and  Hartnack  objectives  Nos.  2  and  7,  giving 
from  30  to  400  diameters.  Such  an  instrument  is  well  adapted  to 
the  work  of  normal  and  pathological  histology,  though  a  condenser  * 
should  be  attached  below  the  stage  and  in  the  optical  axis  for  high- 
power  work  with  immersion  lenses,  and  especially  for  bacteriologi- 
cal research.  The  stand  is  a  rigid  one,  and  if  the  height  of  the 
table  upon  which  it  is  placed  and  the  chair  of  the  observer  be  in  a 
proper  relation,  no  discomfort  need  be  experienced  in  using  the 
microscope  in  the  vertical  position. 

ADJUSTMENT   OF   THE   MICROSCOPE. 

The  microscope  should  be  placed  in  front  of  the  observer,  on  a 
table  of  such  height  that,  when  seated,  he  may,  by  slightly  inclin- 
ing the  head,  and  without  bending  the  body,  bring  the  eye  easily 
over  the  eye-piece.  The  slightest  straining  of  the  body  or  neck 
should  be  avoided.  The  light  should  always  be  taken  from  the 
side,  and  it  matters  little  which  side.  Clouds  or  clear  sky  serve  as 
the  best  source  of  light  for  our  present  work.  Always  avoid  direct 
sunlight.  If  artificial  illumination  be  employed — though  it  is  not 
advised  for  prolonged  investigation — a  small  coal-oil  flame  may  be 
tempered  by  blue  glass. 

ADJUSTMENT    FOR   ILLUMINATION. 

It  will  be  observed  that  there  are  two  mirrors  in  the  circular 
frame  below  the  stage — one  plane  and  the  other  concave.  The 
latter  will  be  employed  almost  exclusively  in  the  work  of  this  vol- 
ume; and  its  curvature  is  such  that  parallel  rays,  impinging  upon 
its  surface,  are  focussed  about  two  inches  from  the  mirror.  It  will 

*  A  non -achromatic  condenser,  after  the  formula  of  Abbe",  of  Jena, 
is  in  quite  general  use  in  this  country.  Its  value  has  been  very  mark- 
edly increased  here  by  the  addition  of  a  rack-and-pinion  motion.  In 
use  for  high-power  work  with  tissues,  it  is  first  placed  so  that  the  plane 
surface  of  the  upper  lens  is  in  contact  with  the  under  surface  of  the 
glass  slip  holding  the  object  to  be  examined.  Light  is  then  reflected 
into  the  condenser  as  usual,  excepting  that  the  plane  mirror  is  employed. 
This  will  give  a  strong  illumination,  but  too  diffuse  for  tissues.  The 
light  is  then  modified  by  diaphragms,  or  by  racking  the  condenser 
downward  until  the  best  effect  is  secured.  For  bacterial  search  the 
strong  illumination  is  employed.  This  gives  prominence  to  the  stained 
microbes,  as  the  other  elements  in  the  field  are  lost  in  the  excess  of  dif- 
fuse light. 


ADJUSTMENT   FOE   FOCUS.  5 

also  be  noticed  that  the  bar,  carrying  the  mirror-fork,  may  be  made 
to  swing  the  mirror  from  side  to  side.  The  work  which  we  are 
about  to  undertake  is  of  such  a  character  as  to  require  the  avoid- 
ance of  oblique  illumination.  We  must,  therefore,  keep  our  mirror- 
bar  strictly  in  the  vertical  position.  If — the  mirror-bar  being  ver- 
tical— a  line  be  drawn  from  the  centre  of  the  face  of  the  mirror, 
through  the  opening  (diaphragm)  in  the  stage,  passing  on  through 
the  objective,  and  so  continued  upward  through  the  body  and  the 
eye-piece,  such  a  line  would  pass  through  the  optical  axis.  The 
centre  of  the  face  of  the  mirror  must  be  in  this  axis.  If,  then,  hav- 
ing gotten  the  mirror-bar  properly  fixed  once  for  all,  the  light  from 
the  adjacent  right  or  left  hand  window  impinges  upon  the  concave 
surface  of  the  mirror,  and  the  latter  be  properly  inclined,  the  rays 
will  pass  through  the  diaphragm  in  the  stage,  and  become  focussed 
a  little  above  the  same.  The  light  rays  will  afterward  diverge, 
enter  the  objective,  and  finally  reach  the  eye  of  the  observer. 

The  /ze/rf  of  view  (as  the  area  seen  in  the  microscope  is  termed) 
we  will  suppose  to  have  been  properly  illuminated — and  by  this  I 
mean  that  it  presents  as  a  clear,  evenly- lighted  area.  Turn  all  the 
factors  spoken  of  out  of  adjustment,  and  proceed  to  readjust. 
Observe  that,  if  the  mirror  be  turned — not  swung — slightly  out  of 
proper  position,  one  side  of  the  field  will  appear  dim  or  cloudy: 
this  must  be  corrected,  and  the  student  must  practise  until  this 
adjustment  becomes  easy  of  accomplishment.  Then  proceed  to  the 

ADJUSTMENT   FOE   FOCUS. 

Observe  that  the  largest  opening  in  the  stage  diaphragm  is  in 
the  optical  axis.  Swing  the  low-power  objective  into  use,  and  rack 
the  tube  up  or  down  until  it  is  about  one  inch  from  the  stage. 

Place  a  mounted  object  upon  the  stage  (a  stained  section  of 
some  organ — say  kidney — will  be  preferable).  Examine  the  field 
through  the  eye-piece,  and  it  will  be  found  obscured  by  the  stained 
object,  and  perhaps  a  dim  notion  of  figure  may  be  made  out.  .Rack 
the  body  down  carefully,  watching  the  eifect.  The  image  becomes 
more  and  more  distinct  until,  at  a  certain  point,  the  best  effect  is 
secured.  The  object  is  in  focus. 

Note  carefully  the  distance  between  the  object  and  the  objective 
(with  the  Hartnack  No.  2  this  will  be  about  seven-eighths  of  an 
inch),  and  hereafter  you  will  be  able  to  focus  more  quickly. 

Having  observed  the  details  of  structure  as  shown  with  the  inch 
objective,  swing  the  high  power  into  use.  Eack  the  tube  down, 
until  the  objective  is  about  one-eighth  of  an  inch  from  the  glass 


6  PRACTICAL    MICROSCOPY. 

covering  the  object.  The  field  is  much  obscured.  Watching  the 
effect  through  the  eye-piece,  rack  the  tube  down  with  great  care 
until  the  image  appears  sharp.  Note  the  distance  with  this  ob- 
jective as  before  with  the  low  power,  probably  about  one-thirty- 
second  of  an  inch.  Then  endeavor,  by  slight  alterations  in  the 
inclination  of  the  mirror,  to  increase  the  illumination.  Turn  the 
diaphragm  so  that  the  light  passes  through  a  small  opening,  and 
note  the  improvement  in  definition.  The  rule  is:  The  higher  the 
power,  the  smaller  the  diaphragm. 

You  have  doubtless  observed,  before  this,  that  you  cannot  con- 
trol the  focussing  as  easily  as  when  the  low  power  was  in  use. 
Slight  movements  of  the  rack-work  produce  marked  changes  in 
definition;  and  it  is  difficult,  with  the  coarse  adjustment  alone,  to 
make  as  slight  movements  as  you  may  desire.  Eecourse  must  be 
had  to  the  fine  adjustment. 

Place  the  tip  of  the  forefinger  (either)  upon  the  milled-head  of 
the  fine  focussing-screw,  and  the  ball  of  the  thumb  against  its  side, 
so  that  the  hand  is  in  an  easy  position.  By  a  little  lateral  pressure 
the  milled-head  may  be  turned  slightly  either  way.  Note  the  effect 
on  the  image.  You  thus  have  the  focussing  under  the  most  per- 
fect control. 

Kemember  that  the  fine  adjustment  is  only  necessary  with  high 
powers,  and  then  only  after  the  image  has  been  found  with  the 
coarse  adjustment. 

METHOD    IN    OBSERVATION. 

The  study  of  objects  under  the  microscope  should  be  conducted 
with  order  or  method. 

The  body  being  in  the  position  before  advised,  so  that  the  sit- 
ting may  be  prolonged  without  fatigue,  let  one  hand  be  occupied 
in  the  maintenance  of  the  focal  adjustment.  It  will  be  found, 
however  flat  an  object  may  seem  to  the  unaided  eye,  that  as  it  is 
moved  so  as  to  present  different  areas  for  examination  (and  with 
the  higher  powers  only  a  small  area  can  be  seen  at  once),  constant 
manipulation  with  the  fine  adjustment  will  be  required.  It  will 
also  be  found  that  even  the  various  parts  of  a  simple  histological 
element — like  a  cell — cannot  be  seen  sharply  with  a  single  focal 
adjustment.  The  forefinger  and  thumb  of  one  hand  must  be  kept 
constantly  on  the  milled-head  of  the  fine  focussing-screw.  Sap- 
posing  the  light  to  be  on  our  right,  we  devote  the  right  hand  to 
the  focussing. 

The  left  hand  will  be  engaged  with  the  glass  slip  upon  which 


MAGNIFYING  POWER  AND  MEASUREMENT  OF  OBJECTS.      7 

the  object  has  been  mounted.  The  forearm  resting  upon  the  table, 
let  the  thumb  and  forefinger  rest  on  the  left  upper  side  of  the 
stage,  just  touching  the  edges  of  the  glass  slip.  The  slightest  pres- 
sure will  then  enable  you  to  move  the  slip  smoothly,  steadily,  and 
delicately. 

Proceed  to  examine  the  object  with  method.  Suppose  a  section 
of  some  tissue  to  be  under  examination— say  one-fourth  of  an  inch 
square.  With  the  high  power  you  will  be  able  to  see  only  a  small 
fraction  of  the  area  at  once.  Commence  at  one  corner  to  observe; 
and  with  the  left  hand  move  the  object  slowly  in  successive  par- 
allel lines,  preserving  the  focus  with  the  right  hand,  until  the  whole 
area  of  the  section  has  been  traversed. 

Practice  will  soon  establish  perfect  co-ordination  of  the  move- 
ments involved,,  and  will  result  in  the  ability  to  work  with  ease, 
celerity,  and  profit. 

CONSERVATION    OF    THE    EYESIGHT. 

The  beginner  should  not  become  accustomed  to  the  use  of  one 
eye  alone,  or  of  closing  either,  in  microscopical  work.  It  will  re- 
quire but  little  practice  to  use  the  eyes  alternately,  and  the  retinal 
image  of  the  unemployed  eye  will  soon  be  ignored  and  unnoticed. 

MAGNIFYING   POWER   AND    MEASUREMENT   OF    OBJECTS. 

The  microscope  is  not,  as  the  beginner  usually  supposes,  to  be 
valued  according  to  its  power  of  magnification,  but  rather  accord- 
ing to  the  clearness  and  sharpness  of  the  image  afforded. 

Magnifying  power  is  generally  expressed  in  diameters.  A  cer- 
tain area  is  by  the  instrument  made  to  appear,  say,  ten  times  as 
large  as  it  appears  to  the  naked  eye.  This  object  has,  then,  its 
apparent  area  increased  one  hundred  times;  but  reference  is  made 
in  describing  such  phenomena  only  to  amplification  in  a  single 
direction.  The  diameter  has  been  increased  ten  times  and  would 
be  expressed  by  prefixing  the  sign  of  multiplication,  e.g.,  X  10. 

A  convenient  unit  of  approximate  measurement  for  the  histol- 
ogist  is  the  apparent  size  of  a  human  red  blood-corpuscle  with  a 
given  objective.  Thirty-two  hundred  corpuscles,  placed  side  by 
side,  would  measure  one  inch;  or,  we  say,  the  diameter  of  a  single 
corpuscle  is  the  thirty-two-hundredth  of  an  inch.  After  consider- 
able practice,  you  will  become  accustomed  to  the  apparent  size  of 
this  object  with  a  certain  objective  and  eye-piece.  This  will  aid  in 
an  approximate  measurement  of  objects  by  comparison,  and  will 
further  give  the  magnifying  power  of  the  microscope.  If  a  cor- 


8  PRACTICAL    MICROSCOPY. 

puscle  appears  magnified  to  one  inch  in  diameter,  it  is  evident  that 
the  instrument  magnifies  thirty-two-hundred  times.  Should  the 
diameter  appear  one-quarter  of  an  inch,  the  power  is  eight  hun- 
dred; one-eighth  of  an  inch,  four  hundred,  etc.  The  instrument 
which  I  have  heretofore  described,  with  the  high  power  in  use  and 
the  tube  withdrawn,  will  present  the  corpuscle  as  averaging  very 
nearly  one-eighth  of  an  inch  in  diameter — x  400.  While  this  gives 
a  gross  idea  of  amplification,  the  method  will  often  prove  inaccurate 
because  of  individual  errors  in  the  estimation  of  proportions. 

Use  of  the  Stage- Micrometer. — From  a  dealer  in  optical  goods 
purchase  a  Rogers  *  glass  stage-micrometer,  ruled  in  hundredths, 
thousandths,  and  five-thousandths  of  an  inch.  Also  procure  from 
the  dealer  in  drawing  instruments  a  two-inch  boxwood  rule  divided 
decimally  to  fiftieths. 

Place  the  micrometer  on  the  stage  of  the  microscope  and  focus 
the  lines.  Then  place  the  rule  also  on  the  stage,  but  just  in  front  of 
and  parallel  with  the  micrometer.  By  a  little  practice,  using  both 
eyes,  the  two  rulings  may  be  seen  simultaneously,  and  by  adjusting 
the  position  of  the  rule,  the  lines  may  be  made  to  appear  superposed. 

Let  us  suppose  that,  with  a  given  eye-piece  and  objective,  the 
thousandth  divisions  on  the  micrometer  correspond  exactly  with 
one  of  the  tenths  of  the  rule.  Keeping  this  in  mind,  remove  the 
micrometer  scale  and  substitute  an  object,  say  a  blood  slide.  Let 
us  again  suppose  that  the  image  of  a  given  red  corpuscle  appears 
to  cover  three  of  the  one-tenth-inch  rulings,  the  latter  scale  having 
been  left  in  position.  It  is  evident  that,  as  we  found  the  value  of 
one  of  the  rule  tenths  to  be,  by  the  micrometer,  the  one-thousandth 
of  an  inch,  the  globule  measures  one- three-thousandth  of  an  inch 
in  diameter. 

The  value  of  the  rule  divisions  must  be  determined  for  each 
objective;  and  a  memorandum  will  then  provide  the  means  of 
quickly  obtaining  a  very  close  approximation  of  the  size  of  objects 
as  viewed  in  the  microscope,  and  at  the  same  time  indicate  the  de- 
gree of  amplification  of  the  instrument  itself. 

SKETCHING    FROM   THE    MICROSCOPE. 

Let  me  most  emphatically  urge  the  practice  of  sketching  in 
connection  with  microscopy.  "  I  am  no  artist/7  or  "  I  have  no  skill 

*  The  micrometer  rulings  of  Professor  Rogers,  of  Cambridge  Univer- 
sity, are  without  doubt  of  surpassing  excellence.  They  are  the  result 
of  many  years  of  unwearying  experimentation  and  are  recognized  stand- 
ards throughout  the  scientific  world. 


SECTION    CUTTING.  9 

In  drawing,"  is  often  the  reply  to  my  advice  in  this  matter.  I 
then  suggest  that  no  special  skill  is  needed  to  begin  with,  only 
patience  and  a  dogged  determination  to  succeed.  The  pictures  in 
the  microscopic  field  have  no  perspective,  and  may  be  reproduced 
in  outline  merely.  Begin  with  simple  tissues,  reserving  intricate 
detail  until  a  short  period  of  practice  gives  the  technique  needed. 
I  do  not  recommend  the  camera  lucida,  as  my  experience  strongly 
impresses  me  with  this  as  a  fact,  that  he  who  cannot  sketch  with- 
out a  camera  will  never  sketch  with  one.  Pencil  drawings  may  be 
very  effectively  colored  with  our  staining  fluids,  diluted  if  necessary. 

PREPARATIONS   OF   TISSUES   FOR   MICROSCOPICAL 

PURPOSES. 

TISSUES   ARE    STUDIED    BY   TRANSMITTED    LIGHT. 

The  microscopical  study  of  both  normal  and  pathological  tis- 
sues is  invariably  conducted  by  the  aid  of  transmitted  light. 

Tissues,  if  not  naturally  of  sufficient  delicacy  to  transmit  light, 
must  in  some  way  be  made  translucent. 

Delicate  tissues  like  omenta,  desquamating  epithelia,  fluids  con- 
taining morphological  elements,  certain  fibres,  etc.,  are  sufficiently 
diaphanous,  and  require  no  preparation.  Such  objects  are  simply 
placed  upon  the  glass  slip,  a  drop  of  some  liquid  added,  and,  when 
protected  by  a  thin  covering  glass,  are  ready  for  the  stage  of  the 
microscope. 

PREPARATION    BY   TEASING. 

The  elements  of  structures  mainly  fibrous — e.g.,  muscle,  nerve, 
ligament,  etc.— are  well  studied  after  a  process  of  separation,  by 
means  of  needles,  known  as  teasing.  A  minute  fragment  of  the 
•organ  or  part  having  been  isolated  by  the  knife  or  scissors  is  placed 
upon  a  glass  slip,  and  a  drop  of  some  fluid  which  will  not  alter  the 
tissue  added.  Stout  sewing-needles,  stuck  in  slender  wood  handles, 
are  commonly  employed  in  the  teasing  process.  The  separation  of 
tissues  is  frequently  facilitated  by  means  of  dissociating  fluids 
which  remove  the  cement  substance. 

SECTION    CUTTING. 

After  having  become  familiar  with  the  various  elementary  struc- 
tures of  animal  tissues,  we  proceed  to  the  study  of  their  relation  to 
organs. 

As  the  teasing  process  is  not  available  with  such  complicated 


10  PRACTICAL    MICROSCOPY. 

structures  as  lung,  liver,  kidney,  brain,  etc.,  we  resort  to  methods- 
of  slicing — i.e.,  section  cutting. 

Sections  must  be  made  of  extreme  tenuity,  in  order  that  the 
naturally  opaque  structures  may  be  illuminated  by  transmitted 
light.  This  becomes  an  easy  matter  with  such  tissues  as  cartilage; 
but  some,  like  bone,  are  much  too  hard  to  admit  of  cutting,  and 
others  are  as  much  too  soft;  so  that  while  certain  tissues  must  be 
softened,  the  majority  must  be  hardened.  Fortunately,  both  of 
these  conditions  may  be  secured  without  in  any  way  altering  the 
appearance  or  relations  of  the  structures.  Hardening  processes, 
from  necessity,  become  a  prominent  feature  in  histologies!  work; 
but  I  propose  here  to  indicate  some  of  the  more  useful  methods  of 
section  cutting,  reserving  the  hardening  processes  for  another  place. 

FREE-HAND    SECTION   CUTTING. 

My  students,  when  ready  for  this  work,  are  provided  with  some 
tissue  which  has  been  previously  hardened.  We  will  take,  for  ex- 


FIG.  3.— FREE-HAND  SECTION  CUTTING. 

ample,  a  piece  of  liver  which  has  been  rendered  sufficiently  firm 
for  our  work  by  immersion  in  alcohol,  and  proceed  to  direct  the 
steps  in  obtaining  suitable  sections  by  the  simple  free-hand  method. 

I  wish  to  strongly  emphasize  the  importance  of  this  mode  of 
cutting.  A  moderate  amount  of  practice  will  render  the  micro- 
scopist  independent  of  all  appliances,  save  those  of  the  most  simple 
character  and  which  are  always  obtainable. 

An  ordinary  razor,  with  keen  edge,  and  a  shallow  dish,  prefers* 


FREE-HAND    SECTION     CUTTING.  11 

bly  a  saucer,  partly  filled  with,  alcohol,  are  required.  The  razor  best 
adapted  to  the  work  is  concave  on  one  side  (the  upper  side  as  seen 
in  Fig.  3)  and  nearly  flat  on  the  other,  although  this  is  largely  u 
matter  of  personal  preference. 

Fig.  3  indicates  the  proper  position  of  the  hands  in  commenc- 
ing the  cut.  I  have  made  the  sketch  from  a  photograph  of  my 
esteemed  colleague,  Dr.  Wesley  M.  Carpenter.  The  student  should 
be  seated  at  a  table  of  such  height  as  to  afford  a  convenient  rest 
for  the  forearms.  A  small  piece  of  tissue  is  held  between  the 
thumb  and  forefinger  of  the  left  hand,  so  that  it  projects  slightly 
above  both.  (In  the  cut,  a  cube  of  tissue,  too  small  to  handle  in 
this  way,  has  been  cemented  to  a  cork  with  paraffin  in  the  manner 
hereafter  described,  and  the  cork  held  as  just  mentioned.)  The 
hand  carrying  the  tissue  is  held  over  the  saucer  of  alcohol.  The 
razor,  held  lightly  in  the  right  hand,  as  seen  in  the  figure,  is,  pre- 
vious to  making  every  cut,  dipped  flatwise  into  the  alcohol,  so  as 
to  wet  it  thoroughly;  and  is  then  lifted  horizontally,  carrying  sev- 
eral drops,  perhaps  half  a  drachm,  of  the  fluid  on  the  concave,  upper 
surface.  The  alcohol  serves  to  prevent  the  section  from  adhering 
to  the  knife,  and  to  moisten  the  tissue.  If  allowed  to  become  dry, 
the  latter  would  be  ruined  by  alterations  of  structure. 

Now  as  to  the  manner  of  moving  the  knife.  Resting  the  under 
surface  upon  the  forefinger  for  steadiness,  bring  the  edge  of  the 
blade  nearest  the  heel  to  the  margin  of  the  tissue  furthest  from 
you.  Then,  entering  the  edge  just  below  the  upper  surface  of 
the  tissue,  with  a  light  but  steady  hold  draw  the  knife  toward  the 
right,  at  the  same  time  advancing  the  edge  toward  the  body.  This 
passes  the  knife  through  the  tissue  diagonally,  and  leaves  the 
upper  surface  of  the  latter  perfectly  flat  or  level.  Eemove  the  piece 
which  has  been  cut  and  repeat  the  operation.  Do  not  attempt  to 
cut  large  or  very  thin  sections  at  first.  A  minute  fragment,  if 
thin,  is  valuable. 

As  the  razor  is  drawn  through  the  tissue,  the  section  floats  in 
the  alcohol;  depress  the  point  of  the  knife  and  the  section  will 
slide  into  the  saucer  of  spirit,  and  thus  prevent  its  injury.  If  it 
does  not  leave  the  knife  readily,  brush  it  along  with  a  camePs-hair 
pencil  which  has  been  well  wetted  with  the  alcohol. 

Proceed  in  the  above  manner  until  the  tissue  is  exhausted, 
when  you  will  have  a  great  number  of  sections,  large  and  small, 
thick  and  thin.  Selecting  the  thinnest,  lift  them  carefully  with  a 
needle,  one  at  a  time,  into  a  small  wide-mouthed  bottle  of  alcohol; 
cork  and  label  for  future  use. 


12  PRACTICAL    MICROSCOPY. 

When  the  work  is  finished,  and  before  the  spirit  has  evaporated 
from  your  fingers — it  is  impossible  to  avoid  wetting  the  skin  more 
or  less — wash  them  thoroughly  and  wipe  dry.  This  saves  the 
roughening  of  the  hands  which  is  apt  to  result  whez  alcohol  has 
been  allowed  to  dry  upon  them  repeatedly. 

SECTION"    CUTTING    WITH    THE    STIRLING    MICROTOME. 

Of  the  numerous  mechanical  aids  to  section  cutting,  I  shall 
mention  only  two  or  three.  One  of  the  earlier  and  better-known 
instruments  is  seen  in  Fig.  4.  The  Stirling  microtome  consists 


FIG.  4.— STIRLING'S  MICROTOME. 

essentially  of  a  short  brass  tube,  into  which  the  tissue  is  fixed, 
either  by  pressure  or  by  imbedding  in  wax.  A  screw  enters  below, 
which,  acting  on  a  plug,  raises  the  contents  of  the  tube.  As  the 
material  to  be  cut  is  raised  from  time  to  time  by  the  screw,  it  ap- 
pears above  the  plate  which  surrounds  the  top  of  the  tube.  This 
plate  steadies  and  guides  the  razor;  and  it  is  evident  that  more 
uniform  sections  may  be  cut  with  this  little  apparatus  than  would 
be  possible  with  nothing  to  support  the  knife,  or  to  regulate  thick- 
ness, beyond  the  unaided  skill  of  the  operator. 

Much  depends  upon  the  manner  in  which  the  material  is  fixed 
in  the  tube  or  well  of  the  microtome.  If  the  tissue  be  of  a  solid 
character,  like  liver,  kidney,  spleen,  many  tumors,  etc.,  it  may  be 


SECTION  CUTTING  WITH  THE  STIRLING  MICROTOME.       13 

surrounded  with  some  carefully-fitted  pieces  of  elder-pin^'*  carrot, 
etc.,  and  the  whole  pressed  evenly  and  quite  firmly  into  the  well. 
A  small  piece  of  tissue  which,  by  cutting,  can  be  made  somewhat 
cubical  in  shape,  may  be  surrounded  by  slabs  of  pith,  carrot,  or 
turnip,  shaped  as  in  Fig.  5.  Indeed,  the  fragments  of  imbedding 
material  can  be  shaped  so  as  to  fit  tissue  of  almost  any  form.  Be- 
fore the  whole  is  pressed  into  the  well  of  the  microtome,  the  bot- 
tom, against  which  the  brass  plug  fits,  should  be  cut  off  square. 

The  wax  method  of  imbedding  is  employed  with  tissues  such  as 
brain,  lung,  soft  tumors,  etc.,  which  might  be  injured  by  the  pre- 
vious treatment.  To  three  parts  of  paraffin  wax  (a  paraffin  candle 
answers  perfectly)  add  one  part  of  vaselin,  and  heat  until  thor- 
oughly mixed.  The  microtome  having  been  previously  warmed — 
standing  upright — is  filled  with  the  imbedding  mixture.  The  piece 


FIG.  5.— MANNER  OF  CUTTING  AND  ARRANGING  PIECES  OP  PITH,  TURNIP,  ETC.,  FOR  SUPPORT- 
ING HARDENED  TISSUE  IN  THE  WELL  OF  A  MICROTOME. 


of  tissue  is  then  carefully  wiped  dry  with  the  blotting-paper  and, 
just  as  the  imbedding  begins  to  congeal  around  the  edges,  is 
pressed  below  ,the  surface  with  a  needle  and  held  until  the  cool 
mixture  fixes  it  in  position.  The  whole  is  now  allowed  to  become 
thoroughly  cold.  By  turning  the  screw,  the  plug  of  wax  is  raised; 
and  it  must  be  gradually  cut  away,  by  sliding  the  knife  across  the 
plate,  until  the  upper  part  of  the  tissue  appears. 

Before  commencing  to  cut  sections — however  the  tissue  may 
have  been  imbedded — provide  yourself  with  a  saucer  of  alcohol  and 
a  camel's-hair  pencil.  Having  wetted  the  knife,  turn  the  screw  so 
that  the  tissue,  with  its  imbedding,  appears  slightly  above  the  plate 
of  the  microtome;  and  then,  resting  the  blade  of  the  razor  on  the 

*  The  pith  from  the  young  shoots  of  Ailantus  glandulosus  (improp- 
erly called  "  Alanthus  "),  gathered  in  early  autumn,  is  the  best  material 
for  this  method  of  imbedding  with  which  I  am  acquainted.  The  wood 
is  easily  cut  from  the  pith,  and  the  latter  is  very  large  and  firm. 


PRACTICAL    MICROSCOPY 


plate  (vide  Fig.  6),  make  the  cut  precisely  as  in  free-hand  cutting. 
The  section  is  then  brushed  off  into  the  saucer,  the  screw  turned  up 
slightly,  the  r<izor  wetted,  and  a  second  cut  made.  These  steps  are 
repeated  until  the  required  number  of  sections  has  been  obtained. 


FIG.  6.—  METHOD  OF  CUTTING  SECTIONS  WITH  THE  STIRLING  MICROTOME. 

The  imbedding  will  leave  the  cuts  as  they  are  floated  in  the 
alcohol.  They  may  now  be  selected,  lifted  with  the  needle  into 
clean  spirit,  and  preserved  as  before  indicated  for  future  opera- 
tions. 

THE   SCHRAUER   MICROTOME. 

Fig.  7  represents  an  improvement  on  the  Stirling  instrument, 
and  a  most  convenient,  practical,  and  inexpensive  microtome  for 
the  physician. 


FIG.  7.— SCHRAUER'S  IMPROVED  STIRLING  MICROTOME. 
With  clamp  for  holding  the  tissue. 

The  tissue,  if  sufficiently  hard,  is  held  in  a  clamp  or  vice  in  the 
well  of  the  instrument,  the  pressure  being  regulated  by  the  side 
screw.  By  this  means  the  necessity  of  imbedding  is  avoided.  If 


THE  AUTHOR'S  LABORATORY  MICROTOMK.  15 

the  tissue  be  too  soft  to  withstand  such  treatment,  it  is  best 
cemented  to  a  cork,  and  the  cork  then  fastened  in  the  clamp.  A 
screw-head  is  cat  upon  a  short  cylinder,  which  works  in  a  corre- 
sponding thread  chased  on  the  inside  of  the  well-tube.  The  short 
cylinder  carries  the  knife-plate,  and,  as  the  latter  is  turned  to  the 
right,  the  whole  descends  and  the  tissue  projects,  ready  to  be  sliced 
•off. 

THE  AUTHOR'S  LABORATORY  MICROTOME. 

For  certain  work,  some  form  of  microtome  becomes  necessary 
in  which  the  operator  is  relieved  from  supporting  the  knife.  Fig. 
8  is  a  sketch  from  such  an  instrument  which  I  have  contrived  and 
which  has  been  in  daily  use  in  my  laboratory  for  over  three  years. 

The  carriage  A,  supporting  the  knife  B,  is  of  solid  cast-iron; 


FIG.  8.— THE  AUTHOR'S  LABORATORY  MICROTOME. 

The  instrument  consists  of  a  very  heavy  cast-iron  bed  upon  which  a  carriage  supporting 
«,  knife  is  made  to  slide.  The  tissue  is  cemented  with  paraffin  (or  held  in  an  adjustable 
clamp  not  shown  in  the  cut)  to  a  table,  which  can  be  raised  by  a  fine  steel  screw.  The 
thickness  of  the  section  to  be  cut  is  controlled  by  turning  the  milled  head  actuating  the 
finely  threaded  screw. 

and  has,  upon  the  under  side,  a  V  guide,  which  fits  into  the  longi- 
tudinal groove  0  of  the  base  D.  Parallel  with  this  groove  is  a 
smooth,  flat  surface,  upon  which  also  travels  the  rib  E  of  the  knife- 
carriage.  A  second  V  has  been  avoided,  in  order  to  diminish  fric- 
tion. The  knife  is  clamped  rigidly  to  the  upper  surface  of  the 
carriage,  by  means  of  a  Willis  tool-holder  consisting  of  a  steel 
plate  F,  a  nut  G,  and  washer  H. 

The  mechanism  for  supporting  and  positioning  the  tissue — not 
shown  in  the  sketch — is  built  upon  a  plate  I,  which  can  be  quickly 
fixed  to  the  body  of  the  microtome  at  the  height  and  lateral  incline 
required  by  the  large  set-screws  J,  J'.  The  mechanism  for  raising 
the  tissue  to  the  knife,  between  the  cuts,  consists  of  a  screw  K,  of 
fifty  threads  to  the  inch,  which,  working  in  thejmt  L,  elevates  the 


16  PRACTICAL    MICROSCOPY. 

bevelled  slide  M,  to  which  the  tissue  N  is  affixed.  An  ether-freez- 
ing attachment  may  be  substituted  for  the  plate  I. 

The  milled-head  0  is  divided  into  one  hundred  parts,  so  that 
each  fraction  of  a  turn  raises  the  tissue  y^  of  an  inch. 

The  knife  should  possess  an  edge  of  the  most  exquisite  keen- 
ness; and  this  holder  admits  the  employment  of  almost  any  cut- 
ting instrument.  In  order  to  the  production  of  the  best  results, 
the  knife  should  be  set  at  the  most  acute  angle  compatible  with 
the  use  of  the  entire  length  of  the  cutting  edge,  from  heel  to  point. 
Both  knife  and  tissue  are  to  be  flooded  with  alcohol  in  ordinary 
work  as  in  free-hand  cutting.  A  drip-pan  is  provided  and  is 
placed  below  the  tissue-carrier.  A  groove  in  the  front  upper  edge 
of  the  base  prevents  the  spirit  from  flowing  over  the  track,  which^ 
mixing  with  the  lubricating  oil  covering  the  latter,  would  interfere 
with  the  delicacy  and  ease  of  the  sliding  motion. 

The  value  of  this  instrument  is  largely  consequent  upon  its, 
great  solidity — the  base  weighing  from  eighteen  to  twenty-five- 
pounds,  with  the  knife-carriage  correspondingly  heavy.  Just  why 
such  weight  and  solidity  are  necessary,  and  contribute  so  largely 
to  our  success  in  cutting  sections,  is  not  at  once  apparent.  The 
microtome  is  now  made  by  Mr.  L.  Schrauer,  of  New  York,  in  twa 
sizes;  the  smaller  carrying  a  knife  fourteen  and  the  larger  eigh- 
teen inches.  A  smaller  pattern  would  present  no  special  advan- 
tages over  microtomes  already  in  use. 

SHARPENING    KNIVES. 

In  the  majority  of  instances  of  failure  to  produce  suitable  sec- 
tions for  microscopical  work,  the  cause  can  be  set  down  to  dull 
knives;  and  I  would  urge  the  student  to  practise  honing  until  able 
to  put  cutting  instruments  in  good  condition.  If  he  will  but  start 
properly,  success  is  sure.  Nine-tenths  of  the  microtomes  are  pur- 
chased because  of  failure  in  free-hand  work  with  a  dull  knife;  but 
no  advantage  will  he  gained  by  a  machine,  if  the  student  be  incapa- 
ble of  keeping  the  knife  up  to  a  proper  degree  of  keenness. 

A  knife  is  a  wedge,  and  for  our  purposes  the  edge  must  be  of 
more  than  microscopical  tenuity — it  being  impossible,  with  the 
microscope,  to  discover  notches  and  nicks  if  properly  sharpened. 

It  is  impossible  to  secure  the  best  results  with  indifferent  tools. 
The  knife  should  be  hard  enough  to  support  an  edge,  but  not  so- 
hard  as  to  be  brittle.  The  proper  temper  is  about  that  given  a 
good  razor. 

We  need  at  least  two  hones — one  comparatively  coarse,  for  re- 


SHARPENING   KNIVES. 


17 


moving  slight  nicks,  and  another  for  finishing.  The  first  part  of 
the  work  is  best  done  by  means  of  a  sort  of  artificial  hone  made 
with  ground  corundum.  These  are  kept  in  stock  by  dealers  in 
mechanics'  supplies,  of  great  variety  in  size  and  fineness.  For 
razors  a  "00"  corundum  slip  will  best  answer.  This  will  very 
rapidly  remove  the  inequalities  from  an  exceedingly  dull  razor.  A 
Turkish  hone  will  be  best  for  finishing.  For  my  large  knives  I 
use  a  third,  very  soft  and  fine  stone,  known  as  water-of-Ayr. 

Let  the  corundum  slip  be  placed  on  a  level  support  (mine  are 
fitted  into  blocks  like  the  carpenter's  oil-stone),  and  cover  the  sur- 
face liberally  with  water.*  The  hones  should  always  be  worked 

FIG.  9. 


FIG.  10. 

FIGS.  9  AND  10.— METHOD  OF  HONING. 

The  knife  is  first  brought  with  its  heel  in  the  position  shown  at  A,  Fig.  9.  It  is  then  drawn 
forward  as  indicated  by  the  curved  dotted  line  until,  at  the  end  of  the  stroke,  the  position  C 
is  attained.  Fig.  10  indicates  the  method  of  turning  the  blade  before  reversing  and  between 
each  stroke. 

wet.  Place  the  knife  flat  on  the  stone  near  the  right  hand  as  at 
A,  Fig.  9.  Draw  steadily  in  the  direction  of  the  curved  dotted 
line — i.e.,  from  right  to  left — holding  the  blade  firmly  on  the  stone 
B  with  slight  pressure  until  the  position  C  is  attained.  Rotate  the 
razor  on  its  back — vide  Fig.  10— so  as  to  bring  the  other  side  on 
the  stone;  and  draw  from  left  to  right.  Observe  that  as  the  knife 
is  drawn  from  side  to  side  (the  edge  invariably  looking  -toward  the 
draw)  it  is  alwTays  worked  from  heel  to  point.  The  amount  of  pres- 
sure may  be  proportioned  to  the  condition  of  the  edge.  If  it  be 

*  A  few  drops  of  glycerin  added  to  the  water  retards  evaporation  and 
appears  to  keep  the  surface  of  the  hone  in  good  condition. 


18  PRACTICAL    MICROSCOPY. 

badly  nicked,  considerable  pressure  may  be  employed ;  while,  as  it 
approaches  keenness,  the  pressure  is  to  be  lessened,  until  the  weight 
of  the  blade  alone  gives  sufficient  friction. 

Repeat  the  process  fifteen  or  twenty  times,  and  examine  the 
blade.  If  the  nicks  are  yet  visible,  continue  honing  until  they  can 
no  longer  be  seen.  Then  draw  the  edge  across  the  thumb-nail. 
Do  this  lightly,  and  the  sense  of  touch  will  reveal  indentations 
which  the  eye  failed  to  recognize.  Continue  the  use  of  the  coarse 
stone  until  the  edge  is  perfect,  as  far  as  the  thumb-nail  test  indi- 
cates. 

The  knife  is  then  to  be  carefully  wiped,  so  as  to  remove  any 
coarse  particles  of  corundum,  and  applied  to  the  wetted  Turkish 
hone  with  precisely  the  same  motions  as  were  employed  in  the  first 
process.  After  a  dozen  or  two  strokes,  examine  the  edge,  by  apply- 
ing the  palmar  aspect  of  the  thumb,  with  repeated  light  touches, 
from  heel  to  point.  This  looks  slightly  dangerous  to  the  novice, 
but  it  is  an  excellent  method  of  determining  the  condition.  Of 
course  actual  trial  with  a  piece  of  hardened  tissue  is  the  best  test. 

Some  most  skilful  technologists  prefer  to  finish  by  stropping. 
I  have  not  used  a  strop  in  my  laboratory  for  over  two  years,  pre- 
ferring to  use  the  knife  as  it  comes,  highly  finished,  from  the 
water-of-Ayr  hone.  If  a  strop  be  employed,  the  leather  should  be 
glued  smoothly  to  a  support  of  wood,  otherwise  the  edge  of  the 
knife  will  become  rounded. 

Stropping  is  conducted  in  the  same  manner  as  honing,  only  the 
edge  of  the  knife  follows  the  stroke  instead  of  leading  it. 

SUPPORTING   TISSUES   FOR   CUTTING. 

Frequently  small  bits  of  tissue  are  required  to  be  cut — pieces 
too  small  to  be  held  with  the  fingers.  I  am  in  the  habit  of  cement- 


FIG.  11.— INSTRUMENT  FOB  SOLDERING  TISSUE  TO  CORK  SUPPORTS  WITH  PARAFFIN. 
It  consists  of  an  awl  handle  of  wood  inf  which  a  short  piece  of  wire,  preferably  copper, 
is  driven  and  bent  as  shown. 

ing  such  tissues  into  a  hole  in  a  bit  of  ailantus,  or  elder-pith,  when 
the  whole  may  be  cut  as  one  mass.  Tissue  is  frequently  cemented 
to  cork  for  convenience  of  holding  in  free-hand  cutting;  or  the 


SUPPORTING   TISSUES   FOR   CUTTING.  19 

cork  may  be  held  in  the  vise  of  the  microtome.  The  edge  of  the 
knife  should  not  be  allowed  to  touch  the  cork. 

Fig.  11  shows  a  simple  little  instrument,  very  convenient  for 
using  paraffin  as  a  cement.  A  piece  of  stout  copper  or  brass  wire 
is  bent  as  indicated,  pointed,  and  driven  into  an  ordinary  awl- 
handle.  Paraffin  wax  possesses  the  very  valuable  property  of  re- 
maining solid  at  ordinary  temperatures,  not  cracking  in  the  cold 
of  winter  or  softening  in  summer.  It  is  unaltered  by  most  re- 
agents, is  easily  rendered  fluid,  and  quickly  solidifies.  As  a  cement, 
it  is  invaluable  to  the  microscopical  technologist. 

Fig.  12  indicates  the  method  of  cementing  a  piece  of  tissue  to  a 


FIG.  12.— MODE  OF  CEMENTING  TISSUE  TO  A  CORK  SUPPORT  WITH  PARAFFIN. 

cork  or  other  support.  The  tissue  having  been  properly  placed, 
the  wire  tool  is  heated  for  a  moment  in  the  alcohol  flame,  and  then 
'touched  to  a  cake  of  paraffin.  The  paraffin  is  melted  in  the  vicin- 
ity of  the  hot  wire,  a  drop  adheres  to  the  latter  and  is  carried  to 
the  edge  of  the  tissue.  In  the  cut  the  wire  tool  is  seen  in  the 
position  necessary  for  cementing  one  edge.  The  wire  being  re- 
moved, the  wax  immediately  cools  and  becomes  solid.  The  other 
sides  are  afterward  cemented  in  like  manner.  The  whole  is  done 
in  less  time  than  is  necessary  to  the  description  of  the  process. 

PREPARATION    OF   TISSUES   FOR   CUTTING,    ETC. 

We  have  already  seen  that  most  animal  tissues  are  unsuitable 
for  the  production  of  thin  sections  until  hardened. 


20  PRACTICAL    MICROSCOPY. 

It  is  also  a  fact,  paradoxical  though  it  may  seem,  that  fresh 
tissues  do  not  present  truthful  appearances  of  structural  elements. 
The  old-school  histologists  insisted  upon  the  presentation  of  struc- 
tures unaltered  by  chemical  substances,  while  the  modern  worker 
has  discarded  such  tissue  with  very  few  exceptions.  Many  descrip- 
tions for  structure  and  growth,  the  result  of  study  upon  fresh 
material,  have  been  proven  by  later  methods  grossly  inaccurate. 

It  is  impossible  to  remove  tissues  from  the  living  animal  and  to 
subject  them  to  microscopical  observation  without,  at  the  same 
time,  exposing  them  to  such  radical  changes  of  environment  as  to 
produce  structural  alterations.  Certain  tissues,  presenting  in  the 
living  condition  stellate  cells  with  the  most  delicate,  though  well- 
defined  branching  processes,  when  removed  from  contact  with  the 
body,  however  expedition  sly,  afford  no  hint  of  anything  resembling 
such  elements,  as  they  are  quickly  reduced  to  simple  spherical  out- 
lines. 

In  short,  it  is  impossible  to  study  fresh  material,  as  such,  with- 
out constant  danger  of  erroneous  conclusions,  as  retrograde  altera- 
tions of  structure  commence  with  surprising  rapidity  the  moment 
a  part  is  severed  from  the  influences  which  control  the  complete 
organism. 

From  what  has  been  said  we  appreciate  the  necessity  of  agents 
which,  when  applied  to  portions  freshly  removed  from  the  animal, 
or  even  before  removal,  shall  instantly  stop  all  physiological  proc- 
esses and  retain  the  elements  in  permanent  fixity. 

Very  much  of  the  human  structure  which  is  available  will  be 
secured  only  after  functional  activities  have  long  ceased,  and  the 
structure  essentially  altered.  We  are,  therefore,  compelled  to  re- 
sort to  the  use  of  material  from  the  lower  animals  in  very  muny 
instances. 

ALCOHOL   HARDENING. 

The  tissue,  whatever  process  may  be  in  contemplation,  having 
been  removed  from  the  body  as  quickly  after  death  as  possible, 
without  washing  or  allowing  contact  with  water  in  any  way,  should, 
with  a  sharp  scalpel,  be  divided  into  small  pieces.  Of  the  more 
solid  organs,  pieces  one-half  inch  square  by  one-fourth  inch  thick 
will  be  sufficiently  small,  and  they  will  harden  rapidly.  The 
smaller  the  pieces  and  the  larger  the  quantity  of  hardening  fluid, 
the  more  quickly  will  the  process  be  completed.  The  volume  of 
fluid  should  exceed  that  of  the  tissue  at  least  twenty  times.  Wide- 
mouth,  well-stoppered  bottles,  from  one  ounce  to  a  pint,  or  even 


CHROMIC-ACID    FIXING   AND   HARDENING.  21 

larger,  are  best;  and  they  should  be  carefully  labelled  and  kept  in 
a  cool  place  with  occasional  agitation. 

Quick  Method. — A  piece  of  any  solid  organ,  say  liver,  spleen, 
pancreas,  kidney,  uterus,  lymph-node,  etc.,  not  larger  than  one-half 
inch  square  by  one-eighth  thick,  may  be  perfectly  hardened  in 
twelve  hours  by  immersion  in  one  ounce  of  ninety-five  per  cent 
alcohol.  No  more  should  be  thus  prepared  than  is  to  be  cut  within 
twenty-four  hours,  on  account  of  the  shrinkage  which  results  after 
the  prolonged  immersion  of  solid  structures  in  strong  spirit. 

After  the  tissue  has  been  one  hour  in  the  above,  it  may  be 
hardened  in  one  or  two  hours  more,  if  transferred  to  absolute 
alcohol.  This  method  is  of  frequent  advantage  in  pathological 
histology. 

Ordinary  Method. — The  method  quite  general  here,  and  in- 
tended to  prevent  shrinkage,  is  as  follows: 

The  organs,  cut  into  pieces  from  one-half  to  three-fourths  of 
an  inch  cube,  are  placed  in  a  mixture  of  alcohol  one  part,  water 
two  parts  (called  in  this  laboratory  "Alcohol  Av)  for  twelve  hours. 
This  removes  the  blood,  and  prepares  the  tissue  for  the  next  mix- 
ture— alcohol  one  part,  water  one  part  ("Alcohol  B  "),  where  it  re- 
mains twenty-four  hours.  The  pieces  are  afterward  removed  to 
ninety-five  per  cent  alcohol  ("Alcohol  C  ").  The  strong  alcohol 
completes  the  hardening,  and  serves  as  a  preservative  until  such 
time  as  sections  may  be  required.  The  process  is  complete  in 
from  two  to  four  weeks,  and  the  material  will  keep  without  deteri- 
oration for  three  or  four  years,  especially  if  the  spirit  be  changed 
occasionally. 

Ordinary  anatomical  specimens  which  have  been  preserved  in 
dilute  alcohol  are  of  no  value  for  our  purpose. 

CHROMIC-ACID    FIXING    AND    HARDENING. 

Chromic  acid  is  a  very  deliquescent  salt,  and  is  best  preserved 
by  making  a  strong  solution  at  once,  and  then  diluting  it  as  may 
be  needed.  A  stock  solution  may  be  made  as  follows : 

Chromic  acid  (crystals),      .         .     25  grammes. 
Water  (distilled  or  rain),    .         .     75  c.cm.     M. 

For  general  use  dilute  20  parts  with  600  parts  pf  water,  which 
gives  a  strength  of  nearly  one-sixth  of  one  per  cent. 

The  tissue,  as  soon  as  secured  and  properly  divided,  is  placed 
in  the  above,  remembering  the  rule  regarding  quantity.  Change 
in  twenty-four  hours  to  fresh  solution,  and  again  on  the  third  day. 


22  PRACTICAL    MICROSCOPY. 

In  seven  .days,  or  thereabout,  change  the  fluid  again.  The  tissue 
must  now  be  watched  carefully,  and  when,  on  cutting  through  a 
piece,  the  fluid  is  found  to  have  stained  the  blocks  completely, 
taking  from  two  to  three,  or  even  four  weeks,  remove  to  a  large  jar 
of  clear  water  and  wash,  changing  the  water  frequently  for  twenty- 
four  hours.  The  washing  having  removed  the  chromic  acid,  the 
tissue  is  further  hardened  in  Alcohol  A,  B,  C. 

The  special  applications  of  this  method,  as  well  as  of  those 
which  will  follow,  are  indicated  in  Part  Third. 

MULLER'S  FLUID  (MODIFIED).* 

Bichromate  of  potash,       ...         25  grammes. 

Sulphate  of  copper,  ....  5 

Water, 1,000   c.cm.      M. 

This  may  be  employed  in  precisely  the  same  manner  as  the 
dilute  chromic-acid  solution. 

DECALCIFYING    PROCESS. 

6$  chromic  acid  solution,  ....       9  parts. 

Nitric  acid,  C.  P., 1  part. 

Water, 90  parts. 

The  earthy  salts  may  be  removed  from  teeth  and  small  pieces  of 
bone  with  a  liberal  supply  of  the  above  in  about  twenty  days.  A 
frequent  change  of  the  solution  will  greatly  facilitate  the  process; 
and  an  occasional  addition  of  a  few  drops  of  the  nitric  acid  may  be 
made,  with  very  dense  bone.  After  the  removal  of  the  lime  salts, 
the  pieces  may  be  preserved  in  alcohol  until  such  time  as  sections 
are  needed,  when  they  may  be  cut  with  the  microtome  without  in- 
jury to  the  knife. 

DISSOCIATING    PROCESS    (W.    STIRLING). 

Artificial  Gastric  Fluid. 

Pepsin, 1  gramme. 

Hydrochloric  acid,        ....        1  c.cm. 
Water, 500  c.cm.     M. 

This  process  depends  for  its  value  upon  the  fact  that  certain 
connective  tissues  are  more  rapidly  dissolved  by  the  fluid  than 
others. 

*  The  original  Mtiller's  fluid  consists  of  the  above  (minus  the  cop- 
per salt)  with  an  addition  of  12.5  grammes  of  sulphate  of  soda. 


CELLOIDIN   INFILTRATION.  23 

BAYBERRY   TALLOW,    HARDENING    OR   INFILTRATING    PROCESS. 

Some  three  years  since,  I  devised  a  method  of  infiltrating  tis- 
sues with  bayberry  tallow.  Tissues  like  lung,  etc.,  which  are  deli- 
cately cellular  and  hence  very  difficult  to  cut,  when  infiltrated  with 
this  material  are  supported  in  such  a  mariner  as  to  render  the  pro- 
duction of  thin  sections  a  very  easy  matter. 

Bayberry  tallow  is  found  in  commerce  in  various  grades.  The 
best  is  white,  clean,  and  of  a  consistency  about  equal  to  that  of 
hard  mutton  tallow.  It  is  instantly  soluble  in  benzol,  and  dis- 
solves rather  slowly  in  alcohol. 

Having  selected  a  piece  of  alcohol-hardened  tissue  for  cutting, 
carefully  wipe  it  dry  with  blotting-paper  and  drop  it  into  a  capsule 
containing  melted  bayberry  tallow.  In  order  to  render  the  tallow 
sufficiently  fluid,  and  yet  prevent  the  heat  from  becoming  great 
enough  to  injure  the  tissue,  the  capsule  should  be  set  over  a  water- 
bath.  Bubbles  immediately  arise  as  the  spirit  is  vaporized  and  the 
tallow  gradually  fills  the  interstices  of  the  tissue.  If  the  latter  be 
of  a  somewhat  dense  character  it  will  be  best,  before  placing  it  in 
the  tallow,  to  allow  it  to  remain  for  an  hour  in  pure  benzol,  which, 
evaporating  at  a  very  low  temperature,  gives  more  ready  admission 
to  the  infiltrating  medium. 

The  length  of  time  required  for  complete  infiltration  will  de- 
pend upon  the  density  and  the  degree  of  heat  employed.  Usually 
from  ten  to  thirty  minutes  will  suffice. 

The  tissue,  having  become  sufficiently  infiltrated,  is  lifted  out 
with  the  forceps,  placed  on  a  cork  support,  and  allowed  to  cool.  It 
is  then  cut,  either  free-handed  or  with  the  microtome,  and  without 
alcohol.  The  dry  sections,  resembling  tallow  or  wax  shavings,  are 
brushed  into  a  saucer  of  pure  benzol,  when  in  a  moment  the  tallow 
will  be  dissolved  from  the  tissue.  The  sections  are  then  lifted  with 
a  needle  singly  into  a  saucer  of  alcohol  to  remove  the  benzol. 
Afterward  they  are  transferred  to  a  bottle  of  spirit,  and  labelled  for 
future  use.  They  will  keep  indefinitely. 

This  process  is  peculiarly  advantageous  with  such  tissues  as 
lung,  pancreas,  cerebellum,  intestine,  etc.,  where  the  structures  re- 
quire support  only  while  they  are  being  cut.  The  infiltrated  blocks 
of  tissue  can  be  kept  dry  until  such  time  as  they  may  be  wanted. 

CELLOIDIN    INFILTRATION. 

Certain  structures  require  permanent  support — i.e.,  not  only 
while  being  cut,  but  during  the  subsequent  handling  of  the  sec- 
tions. The  celloidin  infiltrating  process  is  best  adapted  to  such 


24  PRACTICAL    MICROSCOPY. 

material.  Considerable  time  is  needed  for  the  successful  employ- 
ment of  the  process,  but  results  can  be  secured  that  cannot  be 
equalled  with  any  other  method. 

Celloidin  is  the  proprietary  name  of  a  sort  of  pyroxylin,  very 
soluble  in  a  mixture  of  ether  and  alcohol,  producing  a  collodion. 
If  thick  collodion  be  exposed  for  a  few  moments  to  the  air  it  be- 
comes semi-solid — not  unlike  boiled  egg-albumen;  and  to  this  prop- 
erty is  due  the  value  of  a  solution  of  celloidin  in  histology.  It  may 
be  used  as  follows : 

To  a  mixture  of  equal  parts  of  ether  and  alcohol  add  celloidin  * 
until  the  thickest  possible  solution  has  been  obtained. 

A  piece  of  alcohol-hardened  tissue  having  been  selected  and 
kept  for  the  preceding  twenty- four  hours  in  a  mixture  of  equal 
parts  of  alcohol  and  ether,  is  placed  in  about  an  ounce  of  the  solu- 
tion, and  allowed  to  remain  twenty-four  hours.  The  bottle  con- 
taining the  whole  should  be  well  corked  to  prevent  evaporation. 

The  tissue  after  infiltration  is  to  be  placed  on  a  cork  support 
and  allowed  to  remain  in  the  open  air  for  a  few  minutes,  after 
which  it  should  be  plunged  into  a  mixture  of  alcohol  two  parts, 
water  one  part.  Here  it  may  remain  for  twenty- four  hours,  or  un- 
til wanted. 

Cut  in  the  usual  way,  using  a  mixture  of  alcohol  two  parts, 
water  one  part,  for  flooding  the  knife;  the  section  should  be  finally 
preserved  in  the  same  instead  of  pure  alcohol,  which  would  dissolve 
the  celloidin. 

In  infiltrating  the  tissue  with  the  collodion  it  is  best,  especially 
if  it  be  very  dense  in  parts,  to  use,  first,  a  thin  and  subsequently 
the  thick  solution.  A  more  perfect  infiltration  is  often  obtained 
in  this  way.  In  some  cases  I  have  been  obliged  to  continue  the 
maceration  for  several  days.  The  solution  should  be  kept  in  well- 
stoppered  bottles,  as  the  ether  is  exceedingly  volatile.  Should  the 
collodion  at  any  time  become  solid  from  evaporation,  it  may  be 
easily  dissolved  by  adding  the  ether  and  alcohol  mixture. 

The  process  is  of  inestimable  value  where  delicate  parts  are 
weakly  supported,  and  where  it  is  important  to  preserve  the  normal 
relations.  The  gelatin-like  collodion  permeates  every  space,  and 
as  it  is  not  to  be  removed  in  the  future  handling  of  the  sections, 
it  affords  a  support  to  portions  that  would  otherwise  be  lost  or  dis- 
torted. It  offers  no  obstruction  to  the  light,  being  perfectly  trans- 
lucent and  nearly  colorless. 

*  I  find,  after  repeated  trial,  that  the  ordinary  soluble  gun-cotton, 
such  as  is  employed  by  photographers,  is  in  no  way  inferior  to  the 
celloidin. 


STAINING   AGENTS    AND    METHODS,  25 

HARDENING    BY    FREEZING,    ETC. 

I  do  not  recommend  the  freezing  process. 

Other  fixing  and  hardening  methods,  which  are  of  special  ap- 
plication only,  will  be  introduced  in  our  future  work  as  occasion 
may  demand. 

STAINING   AGENTS   AND    METHODS. 

STAINING    FLUIDS. 

It  is  a  very  interesting  fact  (and  one  upon  which  our  present 
knowledge  of  histology  largely  depends)  that,  on  examination  of 
tissues  which  have  been  dyed  with  special  colored  fluids,  the  dye 
will  be  found  to  have  colored  certain  anatomical  elements  very 
deeply,  others  slightly,  while  others  still  remain  unstained.  Not 
only  are  different  depths  of  color  thus  obtained,  but  different  tints, 
even  with  a  single  dye,  are  often  presented.  If  a  section  of  some 
animal  tissue  be  immersed  in  a  mordanted  solution  of  logwood,  for 
example,  besides  the  different  depths  of  blue  which  are  communi- 
cated to  certain  parts,  other  elements  present  pink  and  violet  tints 
in  various  shades. 

The  rule  concerning  the  selection  of  dyes  seems  to  be  that  those 
elements  of  a  tissue  which  are  the  most  highly  endowed  physiolog- 
ically take  the  staining  most  readily.  The  minute  granules  of 
nuclei  are  so  deeply  stained  in  the  logwood  dye  as  to  appear  almost 
black.  The  nuclei  are  plainly  stained,  while  the  limiting  mem- 
brane of  cells  is  usually  but  slightly  colored.  Old,  dense  connective 
tissues  stain  feebly,  or  fail  entirely  to  take  color.  The  differen- 
tiation is,  without  doubt,  due  to  chemical  action  between  the  ele- 
ments of  the  dye  and  those  of  the  tissue. 

A  very  great  number  and  variety  of  materials  have  been  used 
for  histological  differentiation,  and  a  simple  enumeration  of  them 
all  would  very  nearly  fill  the  remainder  of  our  pages.  It  will  be 
found,  however,  that  leading  histologists  confine  themselves  to  two 
or  three  standard  formulas  for  general  work.  I  shall  notice  only 
those  methods  which  have  been  thoroughly  demonstrated  by  years 
of  employment  as  best  for  the  purpose  suggested.  Special  cases 
will  require  special  treatment,  which  will  be  indicated  in  proper 
•connection. 

HuEMATOXYLIN*    STAINING   FLUID. 

To  about  eight  fluid- ounces  of  a  hot,  saturated  aqueous  solution 
of  common  alum,  contained  in  a  porcelain  caspule,  add,  a  few  grains 

*  The  coloring  principle  of  the  haematoxylon  Campechianum. 
Merck's  preparation  should  be  used. 


26  PEACTICAL    MICROSCOPY. 

at  a  time,  one  drachm  of  hcematoxytin,  with  constant  stirring., 
Boil  over  the  spirit-lamp  very  slowly  for  fifteen  minutes.  Add 
sufficient  water  to  compensate  for  evaporation;  and,,  when  cold, 
pour  into  a  wide- mouth  bottle.  Throw  in  a  piece  of  camphor,  say 
30  grains,  allow  the  whole  to  remain  exposed  to  the  air  for  one 
week,  and 'then  filter. 

The  solution  should  always  be  filtered  before  using.  Keep  the 
filter  paper  in  a  funnel,  and  use  it  as  a  stopper  for  the  bottle. 
The  dye  improves  in  strength  of  color  for  two  or  three  weeks. 

Should  the  solution,  which  is  of  a  beautiful  purple  or  violet 
color,  at  any  time  turn  red,  a  small  piece  of  common  chalk  may  be- 
added.  This  will  restore  the  color  by  neutralizing  the  acidity.  A 
few  crystals  of  alum  should  always  be  kept  in  the  bottle  to  insure 
saturation. 

Prepared  as  above,  the  dye  will  keep  perfectly  for  at  least  eight 
months,  and  gives  a  permanent  stain. 

BORAX-CARMINE   STAINING   FLUID. 

To  eight  ounces  of  a  saturated  aqueous  solution  of  borax  (borate 
of  soda)  add  one  drachm  of  the  best  No.  40  carmine  (previously 
rubbed  into  a  paste  with  a  little  water).  In  order  to  insure  satu- 
ration, some  borax  crystals  should  always  be  left  undissolved  at 
the  bottom  of  the  bottle.  Agitate  frequently,  and,  after  twenty- 
four  hours,  add  fifteen  drops  of  liquor  potassw. 

Always  filter  or  decant  before  using.     It  will  keep  indefinitely,, 

improving,  to  a  certain  extent,  with  age. 

• 

EOSIN    SOLUTION. 

Alcohol, 2  ounces. 

Eosin,     .......         1  drachm. 

This  will  give  a  saturated  solution. 

PICRIC-ACID    SOLUTION. 

Picric  acid,     ......         i  ounce. 

Water, 4  ounces. 

The  acid  is  in  excess,  insuring  saturation. 

NITRATE-OF-SILVER    SOLUTION. 

Nitrate  of  silver, 5  grains. 

Distilled  water, 4  ounces. 

If  the  water  be  pure,  light  will  have  no  effect  upon  the  solution. 


STAINING    METHODS.  27 

STAINING   METHODS. 

H^EMATOXYLIN    STAINING    PROCESS. 

You  will  require  for  future  work  a  needle  like  Fig.  13,  several 
saucers,  preferably  of  white  ware;  a  few  watch-glasses — large,  odd 
sizes  are  usually  cheaply  obtainable  at  the  jeweller's;  half  a  dozen 
glass  salt-cellars — small  ones  known  as  "individual  salts;"  and  a 
two- ounce,  shallow,  covered  porcelain  box,  such  as  druggists  use 
for  ointments,  dentifrices,  etc. 

Place  on  the  work-table  (best  located  so  as  to  be  lighted  from 
your  side  and  not  from  the  front)  in  order,  as  in  Fig.  14. 


FIG.  13.— NEEDLE  FOR  LIFTING  SECTIONS,  ETC. 

1.  A  watch-glass,  containing  say  fl.  3  ij.  of  haematoxylin  fluid. 

2.  Saucer,  filled  with  water. 

3.  Salt-cellar,  filled  with  alcohol. 

4.  The  covered  porcelain  box,  containing  about  an  ounce  of  oil 
of  cloves.* 

Select  a  section  from  some  one  of  your  stock  bottles,  lifting  it 
out  with  the  needle,  and  place  it  in  the  baema.  solution.  The  sec- 
tion having  been  taken  from  alcohol  and  transferred  to  an  aqueous 
staining  fluid,  will  twirl  about  on  the  surface  of  the  latter,  inas- 
much as  currents  are  formed  by  the  union  of  the  water  and  the 
spirit. 

"  How  long  shall  I  let  the  section  remain  in  the  haema.?  "  The 
only  answer  I  can  give  is,  "  Until  properly  stained."  Nothing  but 
experience  will  give  you  any  more  definite  information.  Much 
depends  upon  some  peculiar  property  in  the  tissues :  some  stain 
rapidly,  others  stain  very  slowly.  The  strength  of  the  dye  is  an- 
other determining  factor.  Usually  with  the  haema.  formula,  as 
given,  from  six  to  ten  minutes  will  suffice. 

Place  the  needle  under  the  section  (if  the  fluid  be  so  opaque  as 
to  hide  the  tissue,  place  the  watch-glass  over  a  piece  of  white  paper 
or  a  bit  of  mirror)  and  gently  lift  it  out;  drain  off  the  adhering 
drop  of  dye  on  the  edge  of  the  glass,  and  drop  into  the  saucer  of 
water.  Here  we  can  judge  as  to  the  color,  and  we,  perhaps,  find  it 

*  The  oil  of  bergamot  must  be  used  for  clarifying  sections  which 
have  been  infiltrated  with  collodion,  as  the  clove  oil  is  a  solvent  of  the 
pyroxyline. 


28 


PRACTICAL    MIC  ROSCO  P  Y. 


to  be  of  a  light  purple — too  light ;  so  you  may  return  it  to  the 
haema.  for  another  period  of  two  or  three  minutes,  which  will  prob- 
ably give  sufficient  depth. 

As  the  section  floats  on  the  washing  water,  you  will  notice  that 
the  latter  will  be  colored  by  the  dye,  some  of  which  leaves  the  tis- 
sue. Allow  the  water  to  act  until  no  more  color  comes  out.  The 
tint  of  the  section  changes  from  purple  to  violet,  and  the  water 
must  be  allowed  to  act  until  the  change  is  complete.  Again,  you 
will  remember  that  this  dye  contains  alum,  and  if  you  hurry  the 
washing  you  will  undoubtedly  find  crystals  covering  your  specimen 
after  it  has  been  mounted.  From  five  to  ten  minutes  will  complete 
the  washing. 

If  you  were  to  examine  your  section  at  this  stage,  you  would 
find  it  opaque,  and  as  we  are  obliged  to  study  our  objects  mainly 
by  transmitted  light,  we  must  find  some  means  of  securing  'trans- 
lucency.  The  essential  oils  are  used  for  this  purpose,  oil  of  cloves 
being  commonly  employed.  Lift  the  section  from  the  water  with 
the  needle;  let  it  drain  a  moment,  and  then  drop  it  into  the  alco- 
hol with  which  the  salt-cellar  was  filled.  The  object  of  this  bath 
is  the  removal  of  the  water  from  the  tissue,  and  this  will  be  ac- 
complished in  from  five  to  ten  minutes.  Again  lift  the  section 
and  place  it  in  the  oil  of  cloves.  The  tissue  floats  out  flat,  and  in 
a  few  minutes  sinks  in  the  oil. 

We  might  proceed  to  the  examination  of  the  stained  section; 
but  I  shall  ask  you  to  let  it  remain  in  the  oil,  covering  the  box 
carefully  to  exclude  our  great  enemy,  the  dust,  until  we  have 
learned  more  about  staining. 


FIG.  14.— DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  STAINING  WITH  THE  H^MATOXYLIN 

SOLUTION. 

To  recapitulate:  The  essential  steps  in  the  haema.  process  are: 

1.  Staining  the  tissue — haema. 

2.  Washing — water. 

3.  Dehydrating — alcohol. 

4.  Rendering  translucent— oil  of  cloves. 


STAINING    METHODS.  29 

As  the  section  is  put  in  the  dye,  care  should  be  taken  to  so  float 
it  out  that  it  may  not  be  curled.  This  is  easily  done  with  the 
needle.  After  the  alcohol  bath,  however,  this  becomes  difficult,  as 
the  tissue  is  rendered  stiff  by  the  removal  of  the  water. 

This  is  the  simplest  and  best  of  all  methods  for  general  work, 
and  you  are  advised  to  master  every  detail  of  the  process.  After 
reading  the  directions  which  I  have  given,  and  having  never  seen 
the  work  actually  done,  you  will  not  be  singular  if  you  conclude 
the  staining  of  tissues  to  be  a  tedious  and  slow  process;  but  after  a 
month's  work  you  will  be  able  to  stain  fifty  different  sections  in 
half  an  hour,  and  have  them  ready  for  mounting. 


H.EMATOXYLIN    AND    EOSIN.       DOUBLE    STAINING. 

Very  beautiful  and  valuable  results  in  differentiation  are  ob- 
tained by  staining  first  with  haema.  and  subsequently  with  eosin. 
Eosin  is  a  salt  of  resorcin,  staining  most  animal  tissues  pink,  and  it 
affords  with  the  haema.  a  good  contrasting  color.  The  tissue  is  to 
be  stained  in  haema.  and  washed  in  water  as  usual ;  then  it  is  placed 
in  the  eosin  solution,  and  afterward  washed  again.  The  subse- 
quent treatment  is  as  with  the  plain  haema.  process,  viz.,  dehydra- 
tion with  alcohol,  after  which  the  oil  of -cloves. 


FIG.  15.— DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  DOUBLE  STAINING  WITH  KEMA.  AND 

EOSIN. 

The  diagram,  Fig.  15,  shows  the  process  complete: 

1.  Watch-glass  with  haema. 

2.  Saucer  with  water. 

3.  Watch-glass  two-thirds  filled  with  water,  with  five  drops  of 
eosin  solution  added. 

4.  Saucer  containing  water. 

5.  Salt-cellar  filled  with  alcohol. 

6.  Covered  oil-dish. 

The  eosin  stains  very  quickly,  generally  in  about  a  minute. 
Care  should  be  taken  not  to  overstain  with  it,  as  it  cannot  be 
washed  out.  If  the  sections  are  found  at  any  time  to  be  overstained 
with  haema.  the  color  may  be  removed  to  any  desired  extent  by 


PRACTICAL     MICROSCOPY. 

floating  them  in  a  saturated  aqueous  solution  of  alum.    They  must 
afterward  be  washed  in  clean  water. 

BORAX-CARMINE    STAINING    PROCESS. 

Arrange  your  materials  as  in  the  diagram,  Fig.  16. 

1.  Watch-glass  two-thirds  filled  with  the  carmine  fluid. 

2.  Saucer  containing  about  an  ounce  of  alcohol. 

3.  Salt-cellar  filled  with  a  saturated  solution  of  oxalic  acid  in 
alcohol. 

4.  Salt-cellar  with  alcohol. 

5.  Porcelain  dish  containing  oil  of  cloves. 

The  carmine  solution  will  stain  ordinarily  in  from  three  to  ten 
minutes.     After  the  section  has  been  for  a  few  minutes  in  the  dye, 


FIG.  16.— DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  STAINING  WITH  BORAX-CARMINE. 


you  will  lift  it  with  the  needle,  drain,  and  transfer  to  the  saucer 
containing  alcohol.  You  will  then  be  enabled  to  determine  whether 
the  section  is  sufficiently  stained;  it  should  be  a  deep,  opaque  red. 
The  alcohol  washes  off  the  section,  removing  the  adhering  solution 
of  carmine. 

The  carmine  must  now  be  fixed  in  the  tissue  or  mordanted;  and 
this  you  proceed  to  do  by  transferring  the  section  to  the  watch- 
glass  of  oxalic-acid  solution.  Notice  the  change  in  color,  from  a 
dull  red  to  a  bright  crimson,  and  when  the  change  is  complete,  lift 
it  into  the  salt-cellar  containing  clean  alcohol.  This  dissolves  out 
the  acid,  which,  if  left,  would  appear  later  on  the  specimen  in  crys- 
tals. Five  minutes  suffice  for  this  washing,  after  which  transfer 
to  the  oil  of  cloves. 

This  process  does  not  give  as  sharp  contrasts  as  the  haema.  and 
eosin,  but  it  is  simpler  and  very  permanent.  It  is  best  to  select 
some  one  process  for  general  work,  and  adhere  to  it.  The  acid  of  the 
carmine  process  must  be  guarded  with  extreme  care,  as  the  small- 
est particle  is  sufficient  to  spoil  the  haema.  solution.  Look  to  it 


MOUNTING    OBJECTS.  31 

that  the  dishes  are  kept  scrupulously  clean,  and  the  same  care 
must  be  bestowed  upon  the  needles,  forceps,  etc. 

You  may,  of  course,  stain  several  sections  at  once,  providing  you 
take  care  to  keep  them  from  rolling  up  or  sticking  together. 

While  the  vessels  which  I  have  recommended  will  be  found  of 
convenient,  proportionate,  and  economical  size  for  general  work, 
larger  ones  are  sometimes  needed ;  and  almost  any  glass  or  porce- 
lain vessel  may  be  impressed  for  duty. 

CARMINE  -AND    PICRIC    ACID    STAINING. 

After  having  washed  the  tissue,  subsequently  to  mordanting 
with  oxalic  acid  in  the  borax-carmine  process,  a  bright  yellow  may 
be  communicated  to  certain  anatomical  elements  by  means  of  picric 
acid.  This  often  gives  a  valuable  differentiation. 

The  sections  are  placed  in  the  picric-acid  solution  and  allowed 
to  remain  for  ten  minutes.  Remove  to  water  one  ounce,  glacial 
acetic  acid  ten  drops  for  a  moment,  to  fix  the  yellow;  after  this 
dehydrate  with  alcohol,  and  clarify  "with  oil  of  cloves  as  usual. 
The  sections  should  be  transferred  to  the  picric  and  acetic  acid  so- 
lutions by  means  of  a  platinum  wire  or  a  minute  glass  rod.  The 
ordinary  needle  would  be  corroded,  and  the  sections  thereby  dis- 
colored. 

MOUNTING    OBJECTS. 

CLEANING    SLIDES    AND    COVERS. 

When  purchasing  slides,  let  me  urge  you  to  get  them  of  good 
quality.  The  regular  size  is  one  by  three  inches,  and  the  edges 
should  be  smoothed.  As  furnished  by  the  dealers  they  are  usually 
quite  clean,  and  only  require  rubbing  with  a  piece  of  did  linen  to 
prepare  them  for  use. 

The  cover- glasses  should  be  thin,  not  over  y^th  of  an  inch, 
called  in  the  trade-lists  "  No.  1."  Circles  or  squares  three-quarters 
of  an  inch  in  diameter  are  generally  convenient.  They  must  be 
thoroughly  cleaned :  Drop  them  singly  into  a  saucer  containing 
hydrochloric  acid.  Then  pour  off  the  acid,  and  let  clean  water  run 
into  the  dish  for  several  minutes.  Drain  off  the  water  and  pour 
an  ounce  of  alcohol  on  the  covers.  Remove  them  one  at  a  time 
with  the  forceps  or  needle,  and  wipe  dry  with  old  linen.*  The 

*  We  are  indebted  to  Professor  Gage,  of  Cornell  University,  for  sug- 
gesting the  use  of  Japanese  tissue  paper  for  wiping  cover-glasses,  lenses, 
etc.  Ordinary  manilla  toilet  paper  is  also  an  excellent  material  for 
such  work. 


32  PRACTICAL    MICROSCOPY. 

glass  may  be  held  between  the  thumb  and  forefinger,  the  linen 
being  interposed.  Very  slight  pressure  and  rubbing  will  complete 
the  process.  The  surface  of  the  glasses  should  be  brilliant,  and 
they  are  to  be  preserved  for  future  use  in  a  dust-tight  box. 

TRANSFERRING    THE   SECTIONS    TO   THE    SLIDE. 

Procure  a  piece  of  either  very  thin  sheet  copper  or  heavy  tin 
foil,  three  inches  long  and  one-half  inch  wide,  and  bend  it  about 
three- fourths  of  an  inch  from  one  end,  making  a  section  lifter  as 
shown  in  Fig.  17. 


FIG.  17.— SECTION  SPOON. 

Strip  of  copper  or  heavy  tin  foil,  best  for  lifting  sections  from  staining  and  other  fluids. 
For  use  in  fluids  which  would  attack  rnetals,  the  spoon  should  be  constructed  from  horn. 

Place  a  clean  slide  on  the  table  before  you  and  with  the  section 
lifter  used  like  a  spoon  dip  up  one  of  the  sections  from  the  clove 
oil.  By  inclining  the  lifter,  the  section  may  be  made  to  float  to 
the  centre  of  the  slide.  A  small  sable  brush  is  often  convenient 
for  coaxing  the  section  off  the  lifter. 

If  it  were  our  present  object  to  simply  examine  the  section,  we 
could  drop  a  thin  cover-glass  on  the  specimen,  and  it  would  be 
ready  for  study.  Such  an  object  would  afford  every  requirement 
for  present  observation,  but  would  not  be  permanent.  The  oil  of 


TRANSFERRING   SECTIONS   TO   THE   SLIDE. 


33 


cloves  would  evaporate  after  a  few  days  and  the  section  be  ruined. 
We  proceed  to  make  a  permanenet  mounting  of  our  object. 

The  clove  oil,  surrounding  the  section  on  the  slide,  is  first  to  be 
removed;  and  it  can  easily  be  done  by  means  of  blotting-paper. 
With  a  narrow  slip  of  thin  filter  paper  wipe  up  the  oil,  exercising 
care  not  to  touch  the  section  or  it  will  become  torn.  Proceed  care- 
fully, taking  fresh  paper  until  the  oil  will  no  longer  drain  from  the 


FIG.  18. — METHOD  OF  LABELLING  A  MOUNTED  SPECIMEN. 

section  when  the  slide  is  held  vertically.  With  a  glass  rod  remove 
a  little  of  the  dammar  solution  (vide  formulae)  from  the  bottle  and 
allow  a  drop  of  this  varnish  to  fall  upon  the  section. 

Pick  up  a  clean  cover-glass  with  a  needle,  and  place  it  on  the 
drop  of  dammar.  This  operation  is  seen  in  Fig.  18.  The  point 
of  the  needle  may  be  placed  beneath  the  cover-glass,  the  tip  of  the 


FIG.  19.— MODE  OF  HANDLING  THE  COVER-GLASS  IN  MOUNTING  TISSUES. 

forefinger  pressing  lightly  over  it,  and  you  will  be  enabled  to  carry 
the  thin  glass  wherever  desired. 

As  the  cover  settles  down  the  air  is  pressed  out,  until  finally  the 
section  appears  imbedded  in  the  varnish — the  latter  filling  the  space 
between  the  cover  and  the  slide. 

The  object  is  "  mounted."  You  have  a  permanent  specimen. 
The  slide  must  be  kept  flat,  as  the  dammar  is  soft.  After  some 
3 


34  PRACTICAL    MICROSCOPY. 

weeks,  the  varnish,  around  the  edge  of  the  cover  will  stiffen,  and 
eventually  become  solid.  Do  not  paint  colored  rings  around  the 
specimen.  Nothing  can  present  a  neater  appearance  than  the  sim- 
ple mount,  as  I  have  described  it,  after  having  been  properly  la- 
belled. Labels  seven-eighths  of  an  inch  square  may  be  put  on  one 
or  both  ends,  with  the  name  of  the  object,  date,  method  of  staining, 
or  whatever  particulars  you  may  prefer. 

Specimens  should  be  kept  in  trays  or  boxes  so  as  to  always  lie 
flat. 

CAEE   OF  THE   MICEOSCOPE. 

The  objectives  constitute  the  most  valuable  part  of  the  instru- 
ment. The  lenses  should  never  be  touched  with  the  fingers ;  indeed 
the  same  rule  applies  to  all  optical  surfaces.  When  the  glasses  be- 
come soiled,  they  may  be  cleaned,  but  it  should  be  done  with  great 
care.  While  the  effect  of  a  single  cleaning  would  probably  not  be 
to  the  slightest  appreciable  injury  to  the  glass,  repeated  wiping 
with  any  material,  however  soft,  will  destroy  the  perfect  polish,  and 
result  in  obstruction  of  light  and  consequent  dimness  in  the  field. 
Never  use  a  chamois  leather  on  an  optical  surface,  as  these  skins 
contain  gritty  particles.  Old,  well-worn  linen  and  Japanese  paper 
are  by  far  the  best  materials  for  wiping  glasses.  If  a  lens  be  cov- 
•ered  with  dust,  brush  it  off;  breathe  on  the  surface,  and  wipe 
gently  with  the  linen  or  paper.  Should  you  get  clove  oil  on  the 
front  lens  of  the  objective  (as  frequently  happens  when  examining 
temporary  mounts)  wipe  it  dry  and  then  clean  with  the  linen  moist- 
ened with  a  drop  of  alcohol.  Dammar  varnish  can  be  very  readily 
removed  from  any  surface  after  having  softened  it  with  oil  of  cloves. 
The  front  lens  .of  the  objective,  being  the  only  one  exposed,  is  the 
one  usually  soiled. 

Particles  of  dirt  on  the  objective,  as  I  have  said,  cause  a  dim- 
ness in  the  field — the  image  is  blurred.  Dust  on  the  lenses  of  the 
eye-piece,  however,  appears  in  the  field.  These  lenses  are  readily 
cleaned  by  dusting,  and  wiping  with  the  linen,  after  having  breathed 
on  the  surface.  Never  wipe  a  lens  when  dusting  with  a  camel's- 
hair  brush  will  answer  the  purpose. 

The  microscope  should  either  be  covered  with  a  shade  or  cloth, 
or  put  away  in  its  case,  when  not  in  use.  The  delicate  mechanism 
of  the  fine  adjustment  becomes  worn  and  shaky  if  not  kept  free 
from  dirt. 


PART  SECOND. 


STRUCTURAL   ELEMENTS. 


PEELIMINAKY   STUDY. 

FORM   OF   OBJECTS. 

FROM  a  single  and  hasty  view  of  bodies  under  the  microscope, 
we  are  liable  to  form  erroneous  ideas  of  form.  Either  a  sphere, 
disc,  ellipsoid,  ovoid,  or  cone  may  be  so  viewed  as  to  present  a  cir- 
cular outline.  It  therefore  becomes  important  to  view  objects  in 
more  than  a  single  position.  This  can  easily  be  accomplished  with 
isolated  particles  by  suspension  in  a  liquid.  In  this  way  the  true 
shape  of  a  blood- corpuscle,  e.g.,  may  be  determined. 

Again,  much  information  concerning  the  actual  form  of  bodies 
may  be  gained  by  a  proper  adjustment  of  the  fine  focussing  screw. 
You  may  remember  that  the  depth  of  the  field  of  view  in  the  micro- 
scope is  exceedingly  slight.-  Speaking  accurately,  only  a  single 
plane  can  be  seen  with  a  single  focal  adjustment;  but  by  gradually 
raising  or  lowering  the  tube  of  the  microscope,  the  different  parts 
of  a  body  may  be  focussed  and  studied  and  an  accurate  idea  of 
form  secured. 

With  a  glass  rod  place  a  drop  of  milk,  which  has  previously  been 
diluted  with  three  parts  of  water,  on  a  slide,  and  put  a  cover-glass 
thereon  as  in  Fig.  19.  Focus  first  with  the  low  power  (L).  A  mul- 
titude of  minute  dots  are  observed.  Then  switch  on  the  high 
power  (H),  and  the  dots  will  resolve  into  circular  figures.  Select 
one  of  the  smaller  particles  and,  as  you  raise  the  focus,  the  centre 
of  the  figure  retains  its  brilliancy,  while  the  edges  become  dark  or 
blurred,  showing  convexity.  Reverse  the  focus,  and  the  centre  again 
retains  its  sharpness  long  after  the  edge  has  become  blurred.  The 
figure,  then,  is  a  spheroid.  These  bodies  are  fat-globules.  Parti- 


36  PRACTICAL    MICROSCOPY. 

cles  of  free  fat  always  assume  the  spheroidal  form  when  suspended 
in  a  liquid. 

Note  the  larger  globules;  they  have  become  flattened  by  pres- 
sure of  the  cover-glass. 

Clean  the  slide,  and  make  a  second  preparation  from  the  diluted 
milk — first,  however,  shaking  it  violently  in  a  bottle.  Note  the 
flattened  air-bubbles  among  the  oil-globules.  Observe  that  these 
air-bubbles  have  no  intrinsic  color,  while  the  fat-globules  are  faintly 


Cl 

FIG.  30. — DIAGRAM  SHOWING  THE  EFFECT  OF  AIR-BUBBLES  AND  OIL-GLOBULES  IN  A  MOUNTED 

SPECIMEN  UPON  THE  RAYS  OF    LIGHT. 

The  lines  A,  B  show  the  refraction  of  the  rays  (so  as  to  produce  a  ring  of  color)  by  the 
action  of  two  plano-concave  water  lenses  which  are  formed  by  the  air-bubble. 

The  oil  is  seen  to  correct  the  refraction  of  C  D,  thus  giving  but  little  color  to  the  margin 
of  this  globule. 

yellow.  Observe  the  change  in  the  ring  of  prismatic  color  about 
the  edge  of  the  air-bubble,  as  the  focus  is  altered.  No  such  color 
will  be  seen  in  connection  with  the  oil-globule. 

The  bubbles  assume  various  figures  from  pressure  of  the  cover- 
glass. 

MOVEMENT   OF   OBJECTS. 

Objects  are  frequently  seen  moving  in  the  field  of  the  micro- 
scope, the  movement  being  magnified  equally  with  their  dimensions. 

Thermal  Currents. — When  with  the  previous  specimen,  or  any 
other  fluid  mount,  the  warm  hand  is  brought  close  to  one  side  of 
the  stage,  the  globules  in  the  field  will  be  seen  swimming  more  or 
less  rapidly.  These  currents  are  due  to  the  unequal  heating  of 
the  liquid  under  observation.  The  direction  of  the  current  is  in 
the  reverse  of  its  apparent  motion. 

Browman  Movement. — Place  a  fragment  of  dry  carmine  on  a 
slide;  add  a  drop  of  water,  and  with  a  needle  stir  until  a  paste  is 
formed.  Add  another  drop  of  water,  and  immediately  put  on  the 
cover-glass.  With  H,  note  the  most  minute  particles,  and  observe 
their  peculiar,  dancing  motion.  This  occurs  when  almost  any 
finely-divided  and  generally  insoluble  solid  is  mixed  with  water;  it 
ceases  after  a  short  time.  The  movement  has  been  attributed  to 
several  causes. 


EXTRANEOUS    SUBSTANCES. 


37 


Vital  Movements. — Place  a  drop  of  decomposing  urine  on  a 
slide,  cover  and  focus  with  H.  The  field  contains  innumerable 
minute  spherules  and  rods  (bacteria)  which  are  in  active  motion, 
resembling  somewhat  the  Brownian  movement,  although  suffi- 
ciently distinctive  after  close  observation. 

After  having  rubbed  the  tongue  for  a  moment  against  the  inner 
surface  of  the  cheek,  put  a  drop  of  saliva  on  a  slide,  cover,  and 
focus  H.  Among  the  numerous  thin,  nucleated  scales  and  debris, 
small  granular  spherules — the  salivary  corpuscles — will  be  found. 
Select  one  of  the  last,  centre,  and  focus  H  with  extreme  care. 
The  minute  granules  within  the  cells  are  in  active  motion,  resem- 
bling the  Brownian  movement;  but  with  proper  conditions  the  mo- 
tion may  continue  for  many  hours. 

EXTRANEOUS  SUBSTANCES. 

Before  we  begin  the  study  of  animal  tissues,  I  wish  to  have  you 
become  somewhat  familiar  with  the  appearance  of  certain  objects 


FIG.  21.— EXTRANEOUS  SUBSTANCES. 

A.  Cotton  fibres,  showing  the  characteristic  twist. 

B.  Linen  fibres,  with  transverse  markings  indicating  segments. 

C.  Wool.    The  irregular  markings  are  produced  by  the  overlapping  of  flattened  cells. 
Wool  may  be  distinguished  from  other  hairs  by  the  swellings  which  appear  at  irregular 
intervals  in  the  course  of  the  former. 

D.  Silk.    Smooth  and  cylindrical. 

which  are  frequently,  through  accident  or  carelessness,  and  often 
in  spite  of  the  utmost  care,  found  mixed  with  our  microscopical 


38  PRACTICAL    MICROSCOPY. 

specimens.  Among  the  more  common  objects  floating  in  the  air 
and  gaining  access  to  reagents,  to  subsequently  appear  in  our 
mounted  specimens,  are  the  following : 

Fibres. — Procure  minute  pieces  of  uncolored  linen,  cotton,  wool, 
and  silk.  With  a  needle  in  either  hand,  tease  out  or  separate  a  few 
fibres  on  slides,  add  a  drop  of  water,  and  cover.* 

Starch. — Procure  samples  of  wheat,  corn,  potato  and  arrow- root 
starch,  or  scrape  materials  containing  any  one  of  these  substances 


FIG.  22. — EXTRANEOUS  SUBSTANCES. 

A.  Granules  of  potato  starch. 

B.  Corn  starch. 

C.  Wood  fibres.    The  circular  dots  are  peculiar  to  the  tissue  of  cone-bearing  trees. 

D.  Spiral  thread  from  a  tea  leaf. 

E.  Fragment  of  feather. 

with  a  sharp  knife.     To  a  minute  portion  on  the  slide  add  a  drop 
of  water,  cover,  and  examine  L  and  H. 

Wood  Shavings,  Feathers,  Minute  Insects,  Portions  of  Larger 

*  These  substances,  as  well  as  most  of  those  which  follow  under  the 
same  heading,  may  be  mounted  permanently  as  follows :  Put  the  dry 
material  in  clean  turpentine  for  a  day  or  two,  to  remove  the  contained 
air.  Transfer  to  the  slide,  tease,  separate,  or  arrange  the  elements, 
after  which  wipe  away  the  turpentine  with  strips  of  blotting-paper. 
Add  a  drop  of  dammar  and  place  the  cover-glass  thereon.  The  weight 
of  the  cover  will  be  sufficient  to  press  the  object  flat,  if  it  be  properly 
teased  or  separated.  Although  I  do  not  advise  the  making  of  colored 
rings  around  cover-glasses,  they  may  be  formed  after  first  protecting 
the  dammer  with  a  ring  of  gelatin  (vide  formulae). 


CELLS.  39 

Insects,  Pollen,  etc.,  are  easily  mounted  temporarily  or  permanently 
as  above.  They  are  very  commonly  found  in  urine  after  it  has 
been  exposed  to  the  air,  and  their  recognition  is  very  important. 

Let  me  urge  you  to  become  familiar  with  the  microscopical  ap- 
pearance of  the  commoner  objects  which  surround  us  in  every-day 
life.  The  most  serious  mistakes  have  resulted  from  ignorance  of 
this  subject.  Vegetable  fibres  have  been  mistaken  for  nerves  (!) 
and  urinary  casts,  starch  granules  for  cells,  vegetable  spores  for 
parasitic  ova,  etc. 

STEUCTURAL  ELEMENTS. 

Certain  anatomical  structures,  of  a  more  or  less  elementary  na- 
ture, are  united  in  the  composition  of  organs.  These  structural 
elements  will  with  propriety  first  claim  notice  from  us. 

CELLS. 

A  typical  cell  is  a  microscopical  sphere  of  protoplasm,  consti- 
tuted as  follows  (vide  Fig.  23) : 

A.  Limiting  membrane. 

B.  Cell-body. 

C.  Nucleus. 

D.  Nucleolus. 

.A 


0 

FIG.  23.— ELEMENTS  OF  A  TYPICAL  CELL. 

The  wall  consists  of  an  apparently  structureless  membrane  of 
extreme  tenuity. 

The  cell-body  may  be  either  clear  (jelly-like),  granular,  or  fibril- 
lated. 

The  nucleus  is  a  minute  spherical  vesicle,  with  a  limiting  mem- 


40  PRACTICAL    MICROSCOPY. 

brane  inclosing  a  clear  gelatinous  material,  traversed  by  a  reticulum 
of  fibrillae. 

The  nucleolus  consists  of  a  spherical  granular  enlargement  upon 
the  fibrilla3  of  the  nucleus. 

Deviations  from  the  type  are  most  frequent,  and  vary  greatly 
as  to  form,  number  of  elements,  and  chemical  composition. 


FIG.  24.— A  CELL  NUCLEUS,  WITH  NETWORK  AND  NUCLEOLUS.    DIAGRAMMATIC 

The  typically  perfect  cell  is  rarely  seen  in  human  tissue  on  ac- 
count of  the  length  of  time  which  commonly  elapses  between  death 
and  observation  of  the  structure,  the  delicate  fibrillae  of  the  nuclei 
usually  appearing  as  a  mass  of  granules. 

CELL    DISTRIBUTION. 

The  complex  mechanism  of  the  body  had  its  origin  in  a  single 
cell.  This  preliminary  structure,  endowed  with  the  power  of  pro- 
liferation, became  two  cells.  Two  having  been  produced,  they  be- 
came four;  the  four,  eight;  and  thus  progression  advanced  until 
they  became  countless.  Some  of  these  cells  remained  as  such; 
others  altered  in  form  and  composition  gave  birth  to  muscle,  bone, 
etc.,  etc.  The  study  of  these  processes  belongs  to  physiology. 

The  adult  body  is  composed  largely  of  cells  of  various  forms. 
The  different  physiological  processes,  as  secretion,  absorption,  res- 
piration, etc.,  are  effected  through  the  intervention  of  these  ana- 
tomical elements. 

All  free  surfaces,  within  or  without  the  body,  are  covered  with 
cells.  The  entire  skin,  the  outside  of  organs,  as  lung,  liver,  stom- 
ach, intestine,  brain,  etc.,  etc.;  all  cavities,  as  alimentary  tract, 
heart,  ventricles  of  the  brain,  blood-vessels,  ducts,  all  present  a  su- 
perficial layer  of  cells. 

VARIATION   IN   FORM   OF   CELLS. 

Alteration  from  the  typical  or  spherical  form  is  effected  mainly 
through  pressure  consequent  upon  active  proliferation  of  contigu- 
ous cells,  or  growth  of  surrounding  fibrous  tissues. 


SQUAMOUS  AND   TRANSITIONAL   EPITHELIUM.  41 

FLAT   CELLS. 

If  a  cell  be  subjected  to  pressure  on  two  opposite  sides,  a  flat- 
tening ensues,  and  a  scale-like  element  results.  Flat  cells  are  united 
to  form  a  continuous  structure  in  different  ways. 

SQUAMOUS,   STRATIFIED,   AND   TRANSITIONAL    EPITHELIUM. 

The  simplest  method  of  tissue  production  by  means  of  flat  cells 
is  that  of  superposition,  constituting  squamoux  epithelium.  Cells 
are  placed  one  over  the  other,  generally  without  great  regularity. 
If  regular,  and  in  several  layers,  the  structure  is  called  stratified 
epithelium;  if  only  in  a  few  layers,  it  is  termed  transitional  epi- 
thelium. The  superficial  layer  of  the  skin  affords  an  example  of 


FIG.  25.— SQUAMOUS  CELLS  FROM  BUCCAL  EPITHELIUM 
A.    Typical  cell.    B.    Its  nucleus. 

C.  Union  by  overlapping  forming  laminae. 

D.  Salivary  corpuscles,    x  400. 

;squamous,  stratified  epithelium.     The  bladder,  pelvis  of  the  kid- 
ney, and  vagina  are  lined  with  transitional  epithelium. 

The  thin,  flat  scales  from  the  mouth  may  be  demonstrated  by 
;scraping  a  drop  of  saliva  from  the  tongue  with  the  handle  of  a 
scalpel,  transferring  it  to  the  slide,  and  applying  the  cover.  The 
•size  of  the  drop  of  saliva  should  be  carefully  adjusted  so  as  to  fill 
the  space  between  the  cover-glass  and  slide.  Too  little  will  cause 
the  cover  to  adhere  so  tightly  to  the  slide  as  to  press  the  cells  out 
of  form ;  too  much,  and  the  saliva  flows  over  the  cover  and  soils  the 
objective.  With  a  glass  rod,  place  a  drop  of  the  dilute  eosin  solu- 


42  PRACTICAL    MICROSCOPY. 

tion  on  the  slide,  and  with  a  needle  lead  it  to  the  edge  of  the  salivav 
The  dye  will  pass  under  the  cover  slowly;  and,  gradually,  what- 
ever anatomical  elements  there  may  be  present  will  be  stained.. 
Observe  that  the  nuclei  of  the  flat  scales  first  take  the  dye,  and  ap- 
pear of  a  deep  pink;  while  the  other  portions  are  either  colorless 
or  very  lightly  stained. 

Find  a  typical  field  and  sketch  it  with  pencil,  afterward  tinting 
with  dilute  eosin. 

PAVEMENT    EPITHELIUM. 

When  thin,  flat  cells  are  disposed  in  a  single  layer,  like  tiles,  the 
epithelium  is  termed  pavement  or  tessellated.  These  cells  are  often 
quite  regularly  polygonal  (although  this  obtains  more  frequently 
with  tissue  from  the  lower  animals),  and  they  are  always  connected 
by  their  edges  by  means  of  an  albuminous  cement. 


FIG.  26.— PAVEMENT  EPITHELIUM.    DIAGRAMMATIC. 

This  structure  is  very  extensively  distributed.  Most  serous 
surfaces — e.g..  the  pleurae,  omenta,  mesenteries,  and  peritoneal  sur- 
faces generally— are  so  covered.  The  lining  of  the  heart,  of 
arteries  and  veins,  and  of  lymph  channels  is  constructed  with 
these  cemented  cells.  Blood-capillaries  are  formed  almost  entirely 
of  such  elements. 

The  best  demonstration  is  made  by  coloring  the  cement  which 
unites  the  cells.  If  a  tissue,  covered  with  this  epithelium,  be  placed 
for  a  few  minutes  in  a  solution  of  nitrate  of  silver  a  chemical  union 
ensues;  an  albuminate  of  silver  is  formed  which  blackens  in  the- 
light,  thereby  mapping  out  the  cells  with  great  precision  and  clear- 
ness. 

It  is  nearly  impossible  to  procure  human  tissue  for  this  pur- 
pose, as  the  cement  substance  decomposes  soon  after  death.  The 
mesentery  of  the  frog  affords  a  good  example  of  pavement  cell 


PAVEMENT    EPITHELIUM. 

structure;  and  differs  but  little  from  the  arrangement 
serous  surfaces. 

Kill  a  large  frog  by  decapitation,  and  open  the  abdomen  freely 
by  an  incision  along  the  median  line.  Pull  out  the  intestines  by 
grasping  the  stomach  with  the  forceps.  This  will  expose  the  small 
intestine,  which  you  will  remove,  together  with  the  attached  mes- 
entery, by  means  of  quick  snips  of  the  scissors.  Work  as  rapidly 


Fia.  27.— PAVEMENT  EPITHELIUM  FROM  FROG'S  MESENTERY.    SILVER  STAINING. 

A.  Area  showing  the  outlining  of  the  pavement  cells  by  the  silver-stained  cement  sub- 
stance.   The  nuclei  have  been  brought  out  by  the  carmine.    Minute  stomata  may  be  seen 
between  certain  cells. 

B.  A  blood-capillary  terminating  below  in  an  arteriole.    The  silver  has  outlined  the  en- 
dothelia  of  the  vessels. 

C.  An  area  showing  both  layers  of  the  pavement.    The  deeper  cells  are  faintly  outlined,' 
being  out  of  focus.    The  silver  has  been  deposited  over  the  lower  portion  of  the  specimen, 
nearly  obscuring  the  cement  lines.     X  250. 

as  possible  and  avoid  soiling  the  tissue  with  blood.  Throw  the 
gut  into  a  salt-cellar  filled  with  silver  solution  (vide  formulae),  where 
it  must  remain  for  ten  minutes  covered  from  the  light.  Lift  the 
tissue  from  the  solution  by  means  of  a  strip  of  glass  (or  a  platinum 
wire),  and  throw  into  a  saucer  of  clean  (preferably  distilled)  water, 
changing  the  latter  repeatedly  for  ten  minutes.  After  washing, 
and  while  yet  in  the  water,  expose  to  sunlight  (perhaps  fifteen  min- 


44  PRACTICAL    MICROSCOPY. 

utes)  until  a  brown  tint  is  acquired  which  indicates  the  proper 
staining. 

Proceed  to  stain  the  intestine,  with  mesentery  attached,  with 
borax-carmine  as  directed  for  sections,  excepting  that,  as  the  mass 
is  great,  it  must  be  washed  twice  in  alcohol  after  the  oxalic  acid. 

We  have  allowed  the  mesentery  to  remain  connected  with  the 
gut,  that  the  former  might  not  curl,  as  it  would  have  done  had  it 
been  separate.  The  preparation  having  reached  the  oil  of  cloves, 
proceed  with  a  pair  of  scissors  to  snip  off  a  small,  flat  piece  of  mes- 
entery. Remove  it  to  a  slide,  clean  off  the  oil,  apply  dammar,  and 
cover. 

The  mesentery,  you  have  learned  from  descriptive  anatomy, 
constitutes  a  support  for  blood  and  lymph  vessels  which  are  in 
connection  with  the  intestine.  The  vessels  are  held  together  with 
a  little  delicate  fibrous  (connective)  tissue,  and  are  covered  above 
and  below  with  a  layer  of  pavement  epithelium. 

You  will  observe  prominently  some  dark  lines  (the  larger  ves- 
sels) traversing  the  specimen.  Select  a  thin  spot  between  the  ves- 
sels and  focus  H — you  have  a  picture  like  Fig.  27.  The  field  is 
traversed  by  very  delicate  dark  lines,  indicating  the  position  of  the 
cement  substance;  while  the  nuclei  of  the  cells  are  pink  from  the 
carmine  staining. 

With  the  fine  adjustment-screw  run  the  tube  of  the  microscope 
down  carefully.  The  cement  lines  will  disppear,  and  before  they 
are  completely  out  of  focus,  another  set  of  cells  will  appear  below 
the  first  set.  So  you  may  alternately  bring  into  view  the  upper  and 
under  layers  of  cells  covering  the  respective  sides  of  the  mesentery. 

Observe  the  irregular  shape  of  the  cells.  Note,  also,  that  the 
cells  on  one  side  average  larger  than  those  on  the  other  side.  You 
may  also  notice  in  various  parts  of  the  specimen  blood-vessels  lined 
with  cells  which  are  outlined  with  the  silver  staining. 

Sketch  a  field  showing  the  elements  as  in  Fig.  27,  and  stain  the 
nuclei  with  the  carmine  solution. 

COLUMNAR    CELLS. 

Columnar  Epithelium. 

Columnar  cells  are  found,  generally,  throughout  the  alimentary 
and  respiratory  tracts.  They  also  line  the  cerebral  ventricles,  the 
urinary  and  Fallopian  tubes,  the  uterus,  etc.  This  epithelium  is 
quickly  destroyed  after  death  and  is  difficult  of  perfect  demonstra- 
tion except  in  an  animal  recently  killed. 

Procure  from  the  abbatoir  a  portion  of  the  small  intestine  and 


CILIATED    COLUMNAR   EPITHELIUM.  45 

bronchus  of  a  pig,  and  with  the  curved  scissors  snip  out  small 
pieces  from  the  mucous  surface  of  each.  Macerate  in  one-sixth 
per  cent  of  chromic  acid  for  twenty-four  hours. 

Place  a  piece  of  the  gut  on  a  slide  and,  after  having  added  a 
drop  of  the  acid  solution,  scrape  off  the  mucous  surface  with  a 
knife  and  remove  the  remainder  of  the  gut.  Add  a  cover-glass  and 
focus  H.  You  will  find  cells  in  various  conditions,  from  isolated 
examples  to  small  groups  like  Fig.  28. 


FIG.  28.— COLUMNAR  CELLS  FROM  SMALL  INTESTINE  OP  RABBIT. 

A.  Tapering  attached  extremity. 

B.  A  swollen  goblet  cell. 

C.  Finely-striated  free  border. 

D.  Transparent  line  of  union  between  the  striated  portion  and  the  body  of  the  celL 
X400. 

Observe  that  the  attached  ends  of  the  cells  are  often  small  and 
pointed,  and  that  spheroidal  and  ovoidal  cells  are  frequently  wedged 
in  between  them.  Note  the  free  border:  it  consists  of  striae,  and 
is  separated  from  the  body  of  the  cell  by  a  translucent  line.  This 
appearance  is  also  that  of  the  epithelium  in  the  human  intestine. 

Ciliated  Columnar  Epithelium. 

Prepare,  by  scraping,  a  slide  from  the  mucous  surface  of  the 
pig's  bronchus  (which  has  been  macerating  in  the  chromic  acid). 

Observe  the  cilia  on  the  free  border  of  the  cells.  Interspersed 
between  ciliated  cells,  much-enlarged  individuals  may  be  found, 
the  so-called  beaker,  goblet,  or  mucous  cells. 

The  motion  of  the  cilia  may  be  demonstrated  as  follows : 

Carefully  open  an  oyster  so  as  to  preserve  the  fluid.  On  exam- 
ination you  will  notice  the  leaflets,  shown  in  Fig.  30,  commonly 


46  PRACTICAL    MICROSCOPY. 

called  the  beard.  With  the  scissors  snip  off  a  fragment  of  the  free 
border  of  this  beard,  add  a  drop  of  the  liquid  from  the  oyster,  and 
tease  with  a  pair  of  needles.  Apply  the  cover  and  focus  H. 


FIG.  29.— CILIATED  COLUMNAR  CELLS  FROM  BRONCHUS  OP  PIG.     X  400. 

At  first,  the  individual  cilia  cannot  be  demonstrated  on  ac- 
count of  their  rapid  vibration.  After  a  few  moments,  however, 
the  action  becomes  less  energetic,  and  the  hair-like  appendages 
of  the  cells  are  to  be  plainly  seen. 


3 

FIG.  30.— OYSTER,  OPENED  TO  SHOW  METHOD  OF  PROCURING  LIVING  CILIATED  CELLS. 

A.  The  divided  muscle.    This  must  be  sectioned  before  the  shell  can  be  opened. 

B.  The  heart. 

C.  Liver. 

D.  D.    The  so-called  "  beard."1    These  laminae  are  covered  with  cells  provided  with  cilia ; 
and  a  fragment  of  the  free  border  of  one  of  the  leaflets  may  be  snipped  with  the  scissors, 
and  examined  as  described  in  the  text. 

Of  course  none  of  the  above  objects  are  intended  to  be  perma- 
nent. 


RED   BLOOD-CORPUSCLES. 

SPHEROIDAL    CELLS. 


47 


The  only  cells  which  have,  in  any  very  great  number,  retained 
their  primitive  spheroidal  form  are  the  corpuscles  of  the  blood  and 
of  the  lymphatic  system. 

In  solid  organs,  the  cells,  primarily  spheroids,  often  become 
polyhedral  from  pressure. 

Cells,  developed  spheres,  not  infrequently  send  out  prolonga- 
tions, forming  either  stellate  or  polar  cells  according  to  the  size  of 
the  radiating  processes. 


RED   BLOOD-CORPUSCLES. 


The  human  red  blood-corpuscle  is  a  flattened,  bi  concave  disc, 
one-three-thousand-two-hundredth   of    an   inch  in  diameter.     It 


FIG.  31.— CORPUSCULAR  ELEMENTS  OF  HUMAN  BLOOD. 

A.  Colored  corpuscles  adhering  by  their  sides — rouleaux. 

B.  The  same  crenated. 

C.  The  same  shrunken. 

D.  The  same  having  absorbed  water. 

E.  The  same  still  more  swollen. 

F.  The  same  with  the  plane  C  D,  Fig.  32,  in  focus. 

G.  The  same  with  the  plane  A  B,  Fig.  32,  in  focus. 
H.  Colorless  corpuscles,    x  400. 

presents  a  mass  of  protoplasm  destitute,  as  far  as  the  microscope 
shows,  of  nuclei,  cell-wall,  or  any  structure  whatsoever. 


48  PRACTICAL    MICROSCOPY. 

Certain  changes  in  form  result,  after  removal  from  the  circula- 
tion, viz.  :  1.  They  may  adhere  by  their  broad  surfaces  forming 
columns.  2.  From  shrinkage  they  may  become  crenated.  3.  Still 
further  shrinkage  produces  the  chestnut-burr  appearance.  4. 
From  absorption  of  water  they  may  swell  irregularly,,  obliterating 
the  concavity  of  one  side.  5.  From  continuous  absorption  they 
swell,  forming  spheres  which  are  finally  dissolved.  • 

Wind  a  twisted  handkerchief  tightly  around  the  left  ring-finger  ; 


FIG.  32.—  DIAGRAM  OF  A  COLORED  BLOOD-CORPUSCLE;  SIDE  VIEW,  SHOWING  THE  BI-CONCAVITY. 
A,  B.    Upper  plane  ;  which,  in  focus,  gives  the  appearance  shown  at  G,  Fig.  31. 
C,  D.    Plane  giving  the  appearance  F,  Fig.  31. 

prick  the  end  with  a  clean  needle,  and  squeeze  a  minute  drop  of 
blood  on  a  slide,  add  a  drop  of  saliva,  cover  and  focus  H. 

Observe:  1.  That  considerable  variation  in  size  of  the  red 
blood-corpuscles  exists.  2.  The  color  —  a  delicate  straw  tint.  3, 
That  the  concave  centre  of  the  corpuscles  which  lie  flat  can  be 
made  to  appear  alternately  dark  and  light  according  to  the  focal 
adjustment.  4.  That  the  concavity  is  also  demonstrated  as  tha 
corpuscles  are  turned  over  by  the  thermal  currents.* 

BLOOD-PLATES. 

Minute  corpuscular  elements  in  the  blood  about  one-fourth  the 
size  of  the  red  discs  exist  in  the  proportion  of  about  one  of  the 
former  to  twenty  of  the  latter.  They  are  colorless  ovoid  discs; 
and  are  regarded  by  Osier  as  an  essential  factor  in  the  coagulation 
of  the  blood. 

Prick  the  thoroughly  clean  finger  with  a  needle.  Over  the^ 
puncture  place  a  drop  of  solution  of  osmic  acid  (vide  formulae)  and 
squeeze  out  a  minute  drop  of  blood,  so  that,  as  it  flows,  it  is  cov- 
ered by  the  acid  solution.  This  fixes  the  anatomical  elements^ 
providing  against  further  change.  The  blood,  as  soon  as  drawn^ 
must,  with  the  acid,  be  immediately  transferred  to  a  slide  and  cov- 

*  The  student  is  at  this  time  advised  to  study  the  corpuscular  ele- 
ments of  the  blood  of  such  animals  as  he  may  be  able  to  command. 
The  red  corpuscles  of  mammals  (excepting  the  camelidae)  do  not  vary 
in  appearance  from  those  of  man,  excepting  in  size.  Those  of  birds, 
fishes,  and  reptiles  are  elliptical  with  oval  nuclei.  Corpuscles  of 
blood  of  invertebrates  are  not  colored. 


POLYHEDRAL    CELLS.  49 

ered.     To  provide  against  evaporation,  run  a  drop  of  sweet  oil 
around  the  edge  of  the  cover. 


FIG.  33.— HUMAN  BLOOD  PRESERVED  WITH  OSMIC  ACID. 
A.    Colored  corpuscles.        B.    Colorless  corpuscle. 
C,  C,  C.    Groups  of  plaques.     X  400  and  reduced. 

The  blood-plates  may  be  found,  after  careful  search,  bearing 
the  relation  to  the  red  corpuscles  seen  in  Fig.  33. 

WHITE   OR   COLORLESS   BLOOD-CORPUSCLES. 

The  white  blood-corpuscle  is  a  typical  cell,  spherical  in  form, 
presenting  generally  a  nucleus — often  two  or  more — with  nucleoli. 
In  diameter  about  the  one  twenty-five-hundredth  of  an  inch,  they 
are  usually  found  in  the  blood  in  proportion  of  one  to  three  hun- 
dred to  one  thousand  red  corpuscles.  The  nucleus  of  the  white 
corpuscle  possesses  nearly  the  same  refractive  index  as  the  body  of 
the  cell,  and  is  therefore  difficult  of  demonstration  without  the  use 
of  reagents  or  staining. 

Procure  a  drop  of  pus  from  a  healing  wound,  mix  it  on  a  slide 
with  an  equal  quantity  of  dilute  eosin  solution,  cover,and  examine  H. 

Pus  is  colorless,  containing  spherical  nucleated  corpuscles,  the 
perfect  ones  resembling  exactly  those  found  in  healthy  blood. 
Observe  that  the  nuclei,  some  cells  containing  three  or  even  four, 
are  stained  with  the  eosin.  Minute  pigment-granules  and  fat-glob- 
ules appear  in  many  of  the  pus-cells,  and  others  are  broken  and 
distorted. 

POLYHEDRAL   CELLS. 

With  a  scalpel  scrape  the  cut  surface  of  a  piece  of  liver  from  a 
recently-killed  pig;  place  a  minute  portion  of  the  finer  part  on  a 
4 


50 


PRACTICAL    MICROSCOPY. 


slide;  add  a  drop  of  normal  salt  solution  (ride  formulae) ;  mix  wita 
a  needle,  and  put  on  the  cover-glass. 

With  H  observe,  among  the  numerous  blood-corpuscles/  fat- 
globules,  etc.,  the  polyhedral  liver  cells,  about  twice  or  three  times 


FIG.  34. — GLANDULAR  EPITHELIA. 

A.  A.    Polyhedral  cells  from  human  liver. 

B.  Double  nuclei. 

C.  Cells  from  same  showing  connection  with  a  capillary. 

D.  Same  cells  infiltrated  with  globules  of  fat. 

E.  Cells  from  liver  of  pig  showing  intracellular  network.     X  400. 

the  diameter  of  a  white  blood-corpuscle  (Fig.  34).  Notice  the  large 
spherical  nuclei,  with  nucleoli.  Note,  also,  the  yellow  pigment- 
granules  and  the  fat- globules  in  the  body  of  the  cells.  Masses  of 
these  cells  resemble  somewhat  pavement  epithelium;  they  are  not 
flat  but  polyhedral. 

STELLATE    CELLS. 

When  we  arrive  at  the  study  of  the  skin,  I  shall  show  you  some 
very  beautiful  examples  of  stellate  cells.  I  prefer  to  leave  their 
demonstration  until  you  have  become  more  familiar  with  tissue - 
cutting. 

POLAB   CELLS. 

As  I  have  stated,  spheroids  may  send  off  processes.  These  pro- 
longations may  be  one,  two,  three,  or  more  in  number,  constituting 
unipolar,  bipolar,  tripolar,  etc.,  cells.  The  best  demonstration  is 
made  from  the  nervous  system,  where  these  poles  are  continued  as 
nerves,  etc. 


WHITE   FIBROUS   TISSUE.  51 

From  a  freshly-slaughtered  ox,  sheep,  or  pig  (the  first  being 
the  best)  obtain  a  piece  of  the  spinal  marrow  from  the  region  of 
the  neck.  Cut  it  transversely  into  discs  about  one-eighth  of  an 
inch  thick,  and  place  them  in  the  chromic-acid  fluid  diluted  with 
an  equal  bulk  of  water.  After  thirty-six  hours,  place  one  of  the 
pieces  in  water,  and  with  a  needle  pick  out  minute  fragments  from 
the  anterior  horn  of  the  gray  matter  (refer  to  the  diagram  of  the 
spinal  cord)  and  transfer  them  to  a  slide.  Add  a  drop  of  water 
and  break  the  tissue  into  minute  fragments  by  teasing  with  a  pair 
of  needles.  Examine  from  time  to  time  with  L,  to  note  the  prog- 
ress of  the  teasing.  When  properly  teased,  put  on  the  cover-glass 
and  search  for  large  nucleated  cells  from  which  the  prolongations 
or  horns  are  given  off.  Compare  with  Fig.  123. 

Cells  may  be  classified  as  follows : 

Epithelial — covering-cells,  as  in  skin. 

Endotlielial — lining-cells,  lining  vessels  or  cavities. 

Glandular — constituting  the  parenchyma  of  organs. 

CONNECTIVE    (FIBROUS)    TISSUES. 

Certain  elementary  structures  of  similar  origin  and  mode  of 
development,  and  serving  alike  to  unite  the  various  parts  of  the 
body,  have  been  termed  connective  tissues.  Custom  has  restricted 
the  term,  in  its  every-day  employment,  so  as  to  apply  to  white  fibrous 
tissue  or,  at  least,  to  tissue  which  always  resembles  this  more  closely 
than  any  other,  and  I  shall  so  use  the  expression  in  this  work. 

WHITE    FIBROUS    TISSUE. 

This,  the  connective  tissue  par  excellence,  is  composed  of  ex- 
ceedingly fine  fibrillae  (one-fifty-thousandth  of  an  inch),  which  are 
aggregated  in  irregularly-sized  and  variously-disposed  bundles.  It 
forms  long  and  exceedingly  strong  tendons  connecting  muscle  and 
bone;  its  fibres  interlace,  forming  the  delicate  network  of  areolar 
tissue;  it  forms  thin  sheets  of  protecting  and  connecting  aponeu- 
roses ;  or,  supporting  vessels,  it  permeates  organs  and  sustains  the 
parenchyma  of  glands. 

The  fibres  are  held  together  by  means  of  a  transparent  cement, 
which  may  be  softened  or  dissolved  in  acetic  acid.  They  may  ex- 
ist, as  in  dense  tendons,  without  admixture. 

Cells  are  found  between  the  bundles  of  fibres,  known  as  con- 
nective-tissue corpuscles  or  fibro-blasts.  The  older  and  more  dense 
the  structure,  the  less  frequent  are  these  cells;  while  in  young 


52  PRACTICAL    MICROSCOPY. 

(recent)  connective  tissue,  stained,  the  nuclei  of  the  corpuscles 
constitute  a  prominent  feature  of  the  specimen  under  the  micro- 
scope. 

Having  obtained  a  piece  of  tendon  from  a  recently-killed  bul- 
lock, tease  a  fragment  on  a  slide  in  a  few  drops  of  water.  Select  a 
portion  which  splits  easily  and  separate  the  fibrils  as  much  as  pos- 
sible. Cover  and  examine  H. 


FIG.  35. — CONNECTIVE  TISSUE. 

A.  Teased  fibres  from  a  tendon. 

B.  New  connective  tissue  from  a  cirrhotic  liver. 

C.  Fibrillee. 

D.  Elongate  cells  in  last,  showing  mode  of  formation  of  fibrilla?  from  cell  elements.    X  400. 

Fine,  wavy  fibres  are  seen  composing  the  fasciculae.  If  the 
dissection  has  been  sufficiently  minute,  you  may  succeed  in  de- 
monstrating ultimate  fibrillae.  These  are  best  made  out,  as  at  C  in 
Fig.  35,  where  the  parts  of  a  bundle  have  been  separated  for  some 
distance,  leaving  the  finer  elements  stretching  across  the  interval. 

B  in  Fig.  35  shows  recently-formed  connective  tissue  from  the 
liver,  where  this  structure  had  so  increased  as  to  largely  obliterate 
the  parenchyma  of  the  organ. 

YELLOW   ELASTIC   TISSUE. 

This  tissue  consists  of  coarse  shining  fibres  (averaging  one-three- 
thousandth  of  an  inch)  which  frequently  branch  and  anastomose. 
They  are  highly  elastic.  Under  the  microscope  the  fibres  are  col- 
orless; but  when  aggregated,  as  in  a  ligament,  the  mass  is  yellow. 


YELLOW   ELASTIC   TISSUE. 


FIG.  36. — TEASED  YELLOW  ELASTIC  TISSUE  FROM  THE  LIGAMENTUM  NUCH^E.    x  250. 


FIG.  37.— TRANSVERSE  SECTION  OP  PART  OP  THE  LIGAMENTUM  NUCH.E. 
S.    Sheath  of  the  ligament,  sending  prolongations  within— as  at  T,  T— dividing  the  struc- 
ture into  irregular  bundles  or  fasciculse. 
L.    Lymph  spaces  in  the  connective  tissue. 
A.    Adipose  tissue  in  the  sheath. 
V.    Blood-vessels  in  transverse  section. 
E,  E.    Primitive  fasciculse  of  yellow  elastic  tissue  fibres.     X  250. 


54  PRACTICAL    MICROSCOPY. 

Procure  a  small  piece  of  the  ligament  um  nuchce  of  the  ox,  and 
tease  it  on  the  slide  after  its  having  been  macerated  in  acetic  acid 
for  a  few  moments.  The  acid  softens  the  fibrous  connective  tissue 
and  facilitates  the  teasing  process. 

The  individual  fibres  having  been  isolated,  they  appear  as  in 
Fig.  36.  When  broken,  they  curl  upon  themselves  like  threads  of 
India-rubber. 

This  tissue  is  variously  disposed  throughout  the  body  where 
great  strength  with  elasticity  becomes  necessary.  The  large  arte- 
ries are  abundantly  supplied  with  elastic  fibre,  arranged  in  plates, 
in  alternation  with  muscle.  As  a  network,  it  is  mixed  with  con- 
nective tissue  in  the  skin,  and  in  membranes  generally.  It  con- 
tributes elasticity  to  cartilage  where  the  fibres  form  an  intricate 
network. 

Ligaments  are  composed  largely  of  yellow  elastic  tissue.  Fig. 
37  is  drawn  from  a  portion  of  a  stained  transverse  section  of  the 
ligamentum  subflava. 

A  strong  sheath  of  fibrous  tissue  is  thrown  around  the  whole 
ligament,  a  portion  of  which  is  seen  at  S.  This  sheath  sends  pro- 
longations, T,  T,  into  the  structure,  dividing  it  into  irregular  bun- 
dles, which  support  nutrient  vessels.  The  elastic  fibres  seen  in 
transverse  section,  as  at  E,  E,  are  observed  strongly  bound  together 
with  fibrous  tissue,  which  penetrates  the  smaller  fasciculae,  divid- 
ing them  into  the  ultimate  fibmllce. 

ADIPOSE   TISSUE. 

Adipose  or  fat  tissue  is  a  modification  of  and  development  from 
ordinary  connective  tissue. 

It  originates  in  certain  contiguous  connective-tissue  corpuscles, 
becoming  filled  with  minute  fat-globules.  These  ultimately  coal- 
esce and  form  single,  large  globules,  which  bulge  out  the  cell-bodies 
until  they  become  spheroids;  the  nuclei  at  the  same  time  are  dis- 
placed to  the  periphery.  An  aggregation  of  such  cells  forms  a 
lobule  of  adipose  tissue.  The  cells  are  often  so  closely  packed  as 
to  assume  a  polyhedral  form.  From  malnutrition,  this  fat  may  be 
absorbed,  ordinary  connective  tissue  remaining. 

You  will  bear  in  mind  the  fact  that  whenever  fat  exists  in  a 
condition  of  minute  subdivision,  the  particles  always  assume  the 
globular  form;  and  that  while  adipose  tissue  contains  fat,  fat  alone 
is  not  adipose  tissue. 


ADIPOSE    TISSUE. 


FIG.  38.— CONNECTIVE-TISSUE  CELLS  CONTAINING  FAT— INDICATING  THE  MODE  OP  FORMATION 

OP  ADIPOSE  TISSUE. 

A.  Ordinary  elongate  connective-tissue  cells. 

B.  Same  containing  minute  globules  of  fat. 

C.  Coalescence  of  the  fat-globules  and  displacement  of  the  nucleus. 

D.  Still  greater  increase  of  the  fat.    x  400. 


FIG.  39.— ADIPOSE  TISSUE  FROM  TEASED  HUMAN  OMENTUM.    STAINED  WITH  HJEMA. 

A.  Connective-tissue  framework. 

B.  Cells  distended  with  fat,  showing  fat-crystals. 

C.  Cells  from  which  the  fat  has  been  dissolved  by  ether. 

D.  Cells  faintly  seen  below  the  more  sharply  focussed  plane.     X  400. 


56  PRACTICAL    MICROSCOPY. 


CARTILAGE. 

Cartilage  consists  of  a  dense  basis  substance,  in  which  cells  or 
chondroblasts  are  imbedded.  It  presents  in  three  forms. 

HYALINE   CARTILAGE. 

The  matrix  of  hyaline  cartilage  is  translucent,  dense,  and  ap- 
parently structureless.  Minute  channels  in  certain  instances  and 
delicate  fibrillae  in  others  have  been  demonstrated. 


FIG.  40.— SECTION  OF  HYALINE  CARTILAGE  FROM  A  HUMAN  BRONCHUS. 
The  ground-substance  is  apparently  structureless,  and  its  contains  the  membrane-lined 
excavations  in  which  one,  two,  three,  or  more  cartilage  cells  appear,    These  cells  show  a 
well-marked  intracellular  network,    x  400. 

The  basis  material  contains  excavations,  generally  spherical, 
called  lacunce.  They  are  lined  with  a  delicate  membrane  and  con- 
tain one,  two,  three,  and  perhaps  as  many  as  eight  cells — the  car- 
tilage corpuscles. 

Hyaline  cartilage  is  found  covering  joints  generally,  where  it  is 
termed  articular  cartilage.  It  is  also  found  in  the  trachea,  the 
bronchi,  the  septum  narium,  etc. 

Fig.  40  shows  a  section  from  one  of  the  rings  of  a  large  bron- 
chus. 

FIBRO-CARTILAGE. 

Fibrous  connective  tissue  predominating  largely  in  the  basis 
substance  produces  a  structure  of  great  strength — nbro-cartilage 


ELASTIC    OR   RETICULAR   CARTILAGE.  57 

The  intervertebral  discs  afford  an  example  of  this  variety,  from  a 
section  of  which  Fig.  41  has  been  drawn.     The  membrane  lining 


FlG.  41. — FlBRO-CARTILAGE   FROM  AN  INTERVERTEBRAL  PLATE  OR  DlSC. 

The  ground-substance,  unlike  that  of  the  hyaline  variety,  consists  of  dense  fibrous  tissue 
with  little  calcareous  matter,     x  400. 

the  lacunae  is  much  thicker  than  in  the  previous  example,  and  the 
fibrous  tissue  is  a  very  prominent  feature  of  the  ground-substance. 

ELASTIC    OR   RETICULAR   CARTILAGE. 

As  the  name  implies,  yellow  elastic  tissue  is  an  important  ele- 
ment of  the  ground  substance  of  elastic  cartilage.     It  presents  in 


FIG.  42.— ELASTIC  CARTILAGE  FROM  EAR  OP  BULLOCK. 
"The  ground- substance  consists  largely  of  a  network  of  coarse,  yellow  elastic  tissue.    X  400. 


58 


PRACTICAL     MICROSCOPY. 


the  form  of  a  reticulum,  as  shown  in  Fig.  42.  It  is  not  extensively 
distributed  in  the  human  being,  although  the  cartilages  of  the  ex- 
ternal ear,  Eustachian  tube,  etc.,  are  of  this  variety. 

Cartilage  should  be  hardened  by  the  chromic  acid  and  alcohol 
process.  The  sections  from  which  the  illustrations  have  been 
drawn  were  cut  without  the  microtome.  They  should  be  cut  ex- 
tremely thin,  not  necessarily  large.  We  frequently  succeed  in  get- 
ting good  fields  from  the  thin  edges  of  sections  which  may  be  else- 
where too  thick.  Stain  with  haema.  and  eosin.  The  differentiation 
will  be  excellent.  The  delicate  nutritive  channels  in  the  matrix 
connecting  the  lacunae  may  be  demonstrated  in  the  cartilage  of 
the  sternum  of  the  newt;  the  xiphoid  appendix  is  sufficiently  thin, 
without  sectioning. 

BONE. 

Bone  consists  of  an  osseous,  lamellated  matrix,  in  which  occur 
irregularly-shaped  cavities — lacuna*.  The  latter  are  connected  by 


FIG.  43.— PORTION  OP  A  TRANSVERSE  SECTION  FROM  A  DRIED  FEMUR,  SHOWING  PART  OF  THE 
WALL  OF  AN  HAVERSIAN  SYSTEM. 

A,  A.    Bony  laminae. 

B,  B.    Lacunae. 

C,  C.    Canaliculi.     X  400. 


BONE.  59 

means  of  exceedingly  fine  channels — canaliculi.  The  lacunae  con- 
tain the  bone  corpuscles,  the  bodies  of  which  are  projected  into  the 
canaliculi. 

In  compact  bone,  the  blood-vessels  run  in  a  line  parallel  with 
the  long  axis  of  the  bone,  in  branching  inosculating  channels  (aver- 
aging one-five-hundredth  of  an  inch) — the  Haversian  canals.  The 
lamellae  of  osseous  tissue  are  arranged  concentrically  around  these 
canals.  A  single  Haversian  canal  with  the  lamellae  surrounding 
and  belonging  to  it  constitute  an  Haversian  system. 


FIG.  44.— TRANSVERSE  SECTION  OF  PORTION  OP  A  DRIED  LONG  BONE,  SHOWING  THE  HAVER- 
SIAN SYSTEMS. 

A,  A,  A.    An  Haversian  system. 

B.  Haversian  canal. 

The  lacunae,  canaliculi,  and  Haversian  canals  all  appear  black  in  the  section,  as  they  are 
filled  with  air  and  the  bony  fragments  resulting  from  grinding  of  the  section.     X  60. 

The  lamellae  beneath  the  periosteum  are  not  arranged  as  above, 
but  parallel  with  the  surface  of  the  bone.  These  plates  are  per- 
forated at  right  angles,  and  obliquely  by  blood-vessels  from  the 
periosteum,  as  they  pass  on  their  way  to  the  Haversian  canals. 
These  lamellae  are  also  perforated  by  calcific  connective  tissue — the 
perforating  fibres  of  SJiarpey. 


60  PRACTICAL    MICROSCOPY. 

An  Haversian  canal  contains  (Fig.  44)  an  artery,  a  venule,  lymph 
channels,  and  a  nerve  filament.  The  whole  is  supported  by  con- 
nective-tissue cells  with  delicate  processes.  The  walls  of  the  lymph 
spaces  are  prolonged  into  the  canaliculi  and  thus  placed  in  connec- 
tion with  the  elements  of  the  surrounding  lacunae. 


FIG.  45.— DIAGRAM  OF  AN  HAVERSIAN  CANAL. 

A.  Artery. 

B.  Vein. 

C.  Nerve. 

D.  D,  D.    Lymph  channels. 


Each  lacuna  contains  a  bone  corpuscle,  the  protoplasmic  body 
of  which  sends  prolongations  into  the  contiguous  canaliculi.  In 
the  adult  bone,  the  cell  is  shrunken;  and  the  processes  just  men- 
tioned are  not  readily  demonstrable. 


FIG.  46.— DIAGRAM  OP  A  BONE  LACUNA. 

A,  A.    Ground-substance  of  the  bone. 

B,  B.    Limiting  membrane  of  the  bone  corpuscle  within  the  lacuna. 

C,  Nucleus  and  nucleolus  of  the  corpuscle.  . 

D,  D.    Projection  of  the  cell-body  into  the  canaliculi. 

Fig.  44  has  been  drawn  from  a  section  of  dry  bone  which  has 
been  sawn  as  thin  as  possible,  and  afterward  rubbed  down  on  a 
hone  with  water.  It  is  a  tedious  process,  and  shows  little  but  the 
osseous  matrix.  Bone  should  be  decalcified  for  microscopical 


SPECIAL    CONNECTIVE   TISSUES.  61 

work,  and  it  may  then  be  readily  cut  in  thin  sections  with  a  razor. 
The  process  is  as  follows : 

To  four  ounces  of  the  dilute  chromic-acid  solution  add  a  drachm 
of  C.  P.  nitric  acid.  The  bone,  previously  divided  into  slices  not 
over  one-fourth  of  an  inch  in  thickness,  is  then  placed  in  the  fluid,, 
and  should  be  completely  decalcified  in  a  week  or  ten  days.  Ex- 
amine the  pieces  after  twenty-four  hours  by  puncturing  with  a 
needle.  Should  the  action  proceed  too  slowly,  add  a  few  drops 
more  of  the  nitric  acid  from  time  to  time.  The  bone  eventually 
takes  on  a  green  color.  After  complete  decalcification,  wash  the 
pieces  for  twenty-four  hours  in  clean  water,  and  preserve  them,  un- 
til required,  in  "  B  "  alcohol.  Small  pieces  of  young  bone  may  be 
decalcified  in  a  saturated  aqueous  solution  of  picric  acid.  The  proc- 
ess is  slow,  but  it  leaves  the  tissue  in  excellent  condition. 

Sections  cut  in  the  usual  way  may  be  stained  with  carmine  and 
picric  acid,  and  examined  in  a  drop  of  glycerin.  They  should  not 
after  the  staining  be  placed  in  the  oil  of  cloves,  as  they  would  curl 
and  become  hard.  Transfer  them  to  equal  parts  of  glycerin  and 
water,  from  which  they  are  to  be  carried  to  the  slide.  Add  a  drop 
more  of  the  dilute  glycerin  if  necessary  and  put  on  the  cover-glass, 
carefully  avoiding  air-bubbles.  If  you  desire  to  make  a  permanent 
mounting,  the  edge  of  the  cover  must  be  cemented  to  the  slide. 

Thoroughly  wipe  the  slide,  around  the  cover,  with  moistened 
paper,  until  every  trace  of  glycerin  is  removed.  Then  with  a  sable 
brush,  paint  a  ring  of  zinc  cement  (vide  formulae)  around  the  slide 
just  touching  the  edge  of  the  cover-glass.  Repeat  the  cementing 
in  twenty-four  hours.  A  turn-table  will  be  a  useful  aid  in  this 
work.  Dr.  Carl  Heitzmann,  who  uses  glycerin  as  a  universal  mount- 
ing fluid,  prefers  ordinary  black  (asphalt)  varnish  as  a  cement. 


SPECIAL   CONNECTIVE   TISSUES. 

Connective  Tissue  of  the  Lymphatic  System. — The  matrix  of 
tymphoid  or  adenoid  tissue  consists  of  a  network  of  branching  cells, 
which  support  the  lymph-corpuscles.  It  is  distributed  extensively 
in  organs,  and  where  it  appears  in  stained  sections,  the  lymphoid 
cells  are  so  numerous  as  to  obscure  the  reticulum  almost  entirely. 
The  structure  will  be  minutely  described  in  connection  with  the 
lymphatic  system. 

The  Connective  Tissue  of  the  Central  Nervous  System  (neuro- 
glia)  consists  of  branched  connective-tissue  cells,which  are  supported 


62  PRACTICAL    MICROSCOPY. 

in  an  intimate  network  of  exceedingly  fine  elastic  fibrilla?,  and  will 
receive  attention  later  in  our  work. 

Embryonic  Connective  Tissue  presents  a  homogeneous,  mucoid 
matrix  containing  branched  cells.  It  is  not  found  normally  in  the 
adult. 

MUSCULAK  TISSUE. 

This  tissue  is  found  in  three  varieties :  1.  Non-striated  or  in- 
voluntary; 2.  Striated,  red,  skeletal,  or  voluntary;  3.  Cardiac. 

NON-STRIATED   MUSCLE. 

The  histological  element  of  non-striated  muscle  is  a  spindle- 
shaped  cell  from  one-tenth  to  one-five-hundredth  of  an  inch  long. 
The  cell  body  presents  longitudinal  striae,  and  contains  an  ovoid 
nucleus.  The  nucleus  contains  a  reticulum  which  is  probably  in 


FIG.  47.— WALL  OF  THE  FROG'S  BLADDER,  STAINED  WITH  IL&MA. 

A.  A.    Bands  of  involuntary  muscular  fibre,  recognized  by  the  spindle- cell  sarcous  ele- 
ments. 

B.  A  small  arteriole,  showing  the  same  muscular  element. 

C.  Scattering  muscle  cells. 

D.  Connective-tissue  cells,    x  400. 

connection  with  the  fibrillae,  which  produce  the  longitudinal  stri- 
ation  of  the  body.  The  cells  are  not  infrequently  bifid  at  one  or 
both  extremities.  A  transparent  cement  substance  serves  to 
unite  these  cells  in  forming,  with  connective  tissue,  broad  membra- 


STRIATED    MUSCULAR   TISSUE. 


ility, 


nous  plates,  bundles,  plexuses,  etc.     It  serves  to  afford 
especially  to  the  organs  of  vegetative  life. 

Kill  a  good-sized  frog  by  decapitation,  and  open  the  abdomen 
on  the  median  line.  Fill  the  bladder  with  air,  after  the  introduc- 
tion of  a  blow-pipe  into  the  vent.  Eemove  the  inflated  bladder 
with  a  single  cut  with  the  curved  scissors,  and  place  it  in  a  saucer 
of  water.  Proceed  to  brush  it,  under  the  water,  with  two  camePs- 
hair  pencils  so  as  to  remove  all  of  the  cells  from  the  inner  surface. 
It  will  bear  vigorous  rubbing  with  one  of  the  brushes,  holding  it 
at  the  same  time  with  the  other.  Transfer  to  alcohol  for  ten  min- 
utes, and  afterward  stain  with  haema.  and  eosin.  While  in  the  oil, 
<jut  the  tissue  into  small  pieces,  and  mount  flat  in  dammar.  Ex- 
amine L.  and  H. 

Observe  the  bands  of  involuntary  muscle  crossing  in  various 
•directions.  You  will  distinguish  (Fig.  47)  between  the  muscle  and 
the  connective-tissue  cells  by  their  nuclei. 

STRIATED   MUSCULAR   TISSUE. 

A  skeletal  or  striated  muscle  consists  of  cylindrical  fibres,  one- 
three-hundredth  to  one-six-hundredth  of  an  inch  in  diameter,  and 
one  to  two  inches  long.  These  Drimitive  fibres  are  supported  by  a 


FIG.  48.— DIAGRAM  INDICATING  THE  MINUTE  STRUCTURE  OF  STRIATED  MUSCULAR  FIBRE. 

A,  A.    Sarcolemma. 

B.  Krause's  line  connecting  with  the  sarcolemma  and  dividing  the  fibril  into  compartments. 

C,  C.    The  rod-like  contractile  substance. 

D.  Hensen's  middle  disc. 


64  PRACTICAL     MICROSCOPY. 

delicate,  transparent  sheath — the  sarcolemma.  They  are  aggregated, 
forming  primitive  fasciculi,  which  are  again  united  to  form  the. 
larger  bundles  of  a  complete  muscle.  The  connective  tissue  unit- 
ing the  primitive  fibres  is  termed  endomysium;  while  that  uniting 
the  primitive  bundles  is  the  penmysium. 

The  primitive  muscular  fibres  exhibit  marked  cross  striationa 


FIG.  49.— STRIATED  MUSCULAR  FIBRES  FROM  THE  TONGUE,  TEASED  AND  STAINED  WITH  H.EMA. 

A.  A  fibre,  with  the  muscle  substance  wanting,  from  stretching  during  the  teasing,  the 
sarcolemma  alone  remaining. 

B.  Partly  separated  disc  of  Bowman. 

C.  Ultimate  fibrillae. 

D.  A  blood-capillary,     x  400. 

with  faint  longitudinal  markings,  the  former  being  produced  by 
alternate  dark  and  light  spaces. 

Fig.  48  illustrates  diagrammatically  the  theory  of  the  structure 
of  a  primitive  fibre:  A  indicates  the  sarcolemma.  The  dark  sub- 
stance B,  B  (Krause's  membrane)  divides  the  fibre  completely,  and 
is  united  with  the  sarcolemma.  The  light  spaces  C,  C,  between 
Krause's  membranes,  containing  the  contractile  substance,  are  termed 
the  muscular  compartments  or  discs  of  Bowman.  This  contractile1 


CARDIAC    MUSCULAR   FIBRE.  65 

substance  in  the  living  muscle  is  semi-fluid,  but  in  hardened  tissue 
it  can  be  split  up,  as  indicated  at  0,  into  rods,  the  sarcous  elements. 
A  transparent  line,  D,  in  this  contractile  substance  can  sometimes 
be  demonstrated;  it  is  known  as  Hensen's  middle  disc. 

Macerate  human  muscle,  preferably  that  from  the  tongue,  in 
dilute  chromic  acid  for  twenty-four  hours;  wash,  tease  in  water, 
cover,  and  focus  H.  Fig.  49  was  drawn  from  such  a  preparation. 

The  sarcolemma  is  best  seen  where  the  contractile  substance 
has  been  broken.  The  muscle  nuclei  are  seen  at  various  points 
beneath  the  sarcolemma.  Portions  of  a  fibre  have  beeti  split  off 
transversely  in  places,  indicating  the  discs  of  Bowman.  Sarcous 
elements  are  indicated  where  the  fibre  has  been  split  during  the 
teasing.  The  capillaries  are  arranged  in  a  direction  parallel  to  the 
fibres,  with  frequent  transverse  connections. 

CARDIAC   MUSCULAR   FIBRE. 

It  presents  the  following  characteristics : 

1.  The  fibres  are  smaller  than  those  of  ordinary  skeletal  muscle. 

2.  They  are  striated  both  transversely  and  longitudinally. 

3.  They  branch,  forming  frequent  inosculations. 


FIG.  50.— TEASED  CARDIAC  MUSCULAR  FIBRE. 
Stained  with  haema.     X  400  and  reduced. 


4.  They  are  divided  by  distinct  transverse  lines  into  short  prisms. 

5.  Their  nuclei  are  situated  within  the  fibre. 

6.  They  present  no  distinct  sarcolemma. 

5 


66  PRACTICAL    MICROSCOPY. 

Fig.  50  has  been  drawn  from  fresh  cardiac  muscle,  teased  in 
normal  salt  solution  and  tinted  with  eosin. 

BLOOD-VESSELS. 

Blood-vessels  include  arteries,  arterioles,  capillaries,  venules,  and 
veins.  They  are  all  lined  with  flattened  endothelial  cells  cemented 
by  their  edges;  and  their  walls  are  constructed  from  non-striated 
muscular,  yellow  elastic  and  fibrous  connective  tissues,  in  propor- 
tions varying  according  to  the  size  and  function  of  the  vessel.  Ar- 
teries are  the  active,  while  the  veins  are  comparatively  passive 
agents  in  the  circulation  of  the  blood. 

The  large  arteries  are  eminently  elastic,  from  preponderance  of 


TIG.  51.— TRANSVERSE  SECTION  OP  A  MEDIUM-SIZED  ARTERY.    PARTLY  DIAGRAMMATIC. 

A.  The  endothelial  cells  in  profile. 

B.  Elastic  and  connective  tissue  supporting  the  endothelium. 

C.  The  internal  elastic  lamina  or  fenestrated  membrane.    A,  B,  and  C  constitute  the 
INTIMA  of  the  artery. 

D.  The  MEDIA.    It  consists  of  muscular  and  elastic  tissues  in  alternating  layers. 

E.  Points  to  one  of  the  elastic  layers. 

F.  The  ADVENTITIA.    Loose  connective  tissue,  with  few  elastic  fibres. 

yellow  elastic  tissue;  while  the  arterioles  are  eminently  contractile, 
from  excess  of  muscular  fibre. 

Arteries  possess  three  coats :  the  intima  (internal),  media  (mid- 
dle), and  adventitia  (external). 

Fig.  51  represents  a  medium-sized  typical  artery.  The  intima, 
or  internal  coat  (1),  consists  of  a  layer  of  flattened  endothelial  cells, 
which  rest  upon  fibrous  connective  tissue,  with  a  few  elastic  fibres. 
The  last  is  surrounded  by  a  layer  of  elastic  tissue,  the  elastic  lam- 
ina or  fenestrated  membrane,  which  is  the  external  limit  of  the  in- 
tima. It  presents  in  a  transverse  section  as  a  wavy  (from  contrac- 
tion of  the  media)  shining  line ;  and  is  an  important  element,  from  its 


BLOOD-VESSELS. 


67 


relation  to  certain  abnormalities  of  the  blood-vessels.  The  media 
(2)  consists  of  alternate  layers  of  elastic  and  muscular  tissue.  The 
adventitia  (3)  is  composed  of  fibrous  connective  tissue,  containing 
some  elastic  elements. 

As  we  approach  the  larger  arteries,  the  muscular  tissue  dimin- 
ishes in  quantity  and  the  elastic  tissue  is  increased.  On  the  other 
hand,  the  elastic  element  diminishes  with  preponderance  of  muscle 
as  we  approach  the  smaller  arteries,  until  we  meet  the  arterioles, 
the  walls  of  which  are  made  almost  exclusively  of  involuntary  mus- 
cular fibre. 

The  walls  of  capillaries  consist  of  a  single  layer  of  flattened  en- 
dothelial  cells  cemented  by  their  edges.  The  union  is  not  quite 


FIG.  52.— ISOLATED  BLOOD-CAPILLARIES. 

A.  Plexus  from  a  pulmonary  alveolus,  stained  with  silver,     x  350. 

B.  Capillary  from  omentum,  stained  with  silver  and  hsema.     x  700. 

In  A  the  cells  are  outlined  by  the  silver  ;  while  in  B  the  nuclei  in  addition  are  brought 
out  by  the  haema. 

continuous,  as  minute  openings  (stomata)  are  to  be  seen  at  irregular 
intervals. 

The  walls  of  veins  are  much  thinner  than  those  of  arteries. 
The  intima  presents  an  endothelial  lining,  but  no  fenestrated  mem- 
brane; and  the  line  of  demarcation  between  this  coat  and  the 
media  is  often  indistinct.  The  media  contains  muscular,  but  little 
elastic  tissue;  and  the  adventitia,  usually  the  most  prominent  of 
the  three  coats,  is  composed  largely  of  fibrous  connective  tissue. 

I  shall  defer  the  microscopical  examination  of  blood-vessels 
until  we  meet  them  in  future  sections  of  organs,  as  they  are  best 
studied  in  such  connection. 


PART  THIRD. 


ORGANS, 


THE  SKIN. 

THE  skin  consists  of  (1)  the  epidermis  (or  scarf  skin),  which 
everywhere  covers  and  protects  (2)  the  derma  (corium  or  true  skin). 

The  epidermis  varies  greatly  in  thickness  in  different  locations; 
and  in  the  thicker  portions  several  layers  may  be  differentiated. 
It  is  composed  entirely  of  cells,  while  the  derma  is  fibrous. 

Stratum  Corneum,  )  Hornv  Laver  ^  -2 

Stratum  Lucidum,  f  J       J  ]   g 

sa:  JESS-SB*     Mec^r or  f  1 

Stratum  of  Elongate  (Pigment)  )  J  pq 

Cfe£fc, 

The  stratum  corneum  consists  of  old,  exhausted,  flattened,  and 
desiccated  cells,  which  are  constantly  falling  from  the  entire  sur- 
face of  the  body.  Dandruff  consists  of  impacted  cells  from  this 
source.  Those  portions  most  frequently  exposed  to  friction — e.g., 
the  palms  of  the  hands  and  soles  of  the  feet — are  protected  by  a 
corneous  epidermal  layer  of  great  thickness. 

The  sratum  lucidum,  or  clear  layer,  presents  cells  in  form  not 
unlike  those  in  the  preceding  stratum;  they  are,  however,  trans- 
lucent. This  is  properly  a  part  of  the  previous  stratum,  is  often 
absent,  and  frequently  very  difficult  of  demonstration. 

The  stratum  granulosum,  or  granular  layer,  is  composed  of  flat- 
tened cells  containing  opaque  granules. 

Immediately  beneath  the  last-named   layer,  the  cells  become 


THE    SKIN. 


69 


strikingly  altered  in  form  and  appearance.  The  prickle  cells  are 
polygons  or  compressed  spheroids,  with  large,  oval  nuclei,  and 
minute,  projecting  spines.  By  means  of  these  processes  they  are 
very  firmly  united. 

The  fifth  and  last  (deepest)  layer  of  the  epidermis  is  composed 
of  a  single  rank  of  elongate  cells,  placed  with  their  long  axes  at 
right  angles  to  the  surface  of  the  skin.  These  cells  contain  the 


FIG.  53.—  VERTICAL  SECTION  OF  THE  EPIDERMIS  FROM  THE  PALM  OF  THE  HAND.    STAINED 

WITH  H^MA.  AND  EoSIN. 

A.  Stratum  corneum. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

D.  Prickle  cells  of  rete  mucosum  or  R.  Malpighii. 

E.  Stratum  of  elongate  cells,  the  lower  limit  of  the  epidermis. 

F.  F.    Indicate  the  position  of  two  papillae  of  the  true  skin  or  derma.     X  400. 


pigment  which  gives  the  hue  peculiar  to  the  skin  of  colored  indi- 
viduals. 

The  first  two  layers  of  the  epidermis  constitute,  properly,  the 
horny  layer;  while  the  remaining  three  strata  compose  the  rete 
mucosum  or  rete  Malpigliii. 

The  derma,  corium  or  true  skin,  is  composed  of  dense,  fibrillated 
connective  tissue,  so  formed  as  to  present  minute  elevations  or 


70  PRACTICAL    MICROSCOPY. 

papillae  over  the  entire  surface  of  the  body.  These  papillae  are  cov- 
ered with  a  basement  membrane,  and  are  protected  from  undue 
irritation  by  the  epidermal  layers. 

The  subcutaneous  cellular  tissue  (upon  which  the  true  skin 
rests)  consists  of  fibrillated  connective  tissue  with  elastic  elements, 
from  which  strong  interlacing  bands  are  formed.  These,  in  the 
deeper  parts,  form  septa  which  support  lobules  of  adipose  tissue. 
These  isolated  collections  of  adipose  tissue,  when  elongated  and 


FIG.  54.— VERTICAL  SECTION  OP  THE  DERMA,  OR  TRUE  SKIN. 

A,  A.    Line  of  elongate  cells  belonging  to  the  epidermis. 

B,  B,  B.    Summits  of  three  papillae  of  the  true  skin. 

C,  C,  C.    Portions  of  capillary  loops  in  the  papillae. 

D,  D.    Nerve  loops,  tactile  corpuscles.    X  250. 

placed  vertically  to  the  surface,  constitute  the  fat-columns  of  Sat- 
terthwaite. 

The  blood-vessels  supplying  the  skin  may  be  seen  in  vertical 
sections,  in  the  subcutaneous  tissue.  Branches  from  these  are 
sent  to  the  papillae,  where  they  terminate  in  delicate,  interlacing 
loops  of  capillaries. 

Medullated  nerves  are  also  sent  to  the  papillae ;  and  in  certain 
locations,  they  may  be  seen  to  terminate  in  tortuous  structures — 


THE   HAIES.  71 

the  tactile  corpuscles.     Varicose  nerve  fibrils  have  been  traced  be- 
tween the  cells  in  the  rete  mucosum  of  the  epidermis. 


APPENDAGES   OF   THE   SKIK 

The  appendages  of  the  skin  are   the   hairs,  sebaceous  glands, 
sudoriferous  glands,  and  the  nails. 


THE    HAIRS. 

A  hair,  consisting  of  a  root  and  shaft,  is  constructed  from  elon- 
gate cells  which  are  cemented  together,  and  overlapped  with  cell- 
plates.  The  central  part  of  medullated  hairs  is  composed  of  cubi- 
cal cells,  pigment,  and  occasional  minute  air-bubbles. 

The  root  penetrates  the  stratum  corneum  and  (appearing  to 
have  pushed  the  rete  mucosum  before  it)  passes  through  the  true 


E 

FIG.  55.— TRANSVERSE  SECTION  OF  HAIR,  AND  HAIR-FOLLICLE.    PARTLY  DIAGRAMMATIC. 

A.  Medulla  of  hair. 

B.  Cortex  of  same. 

C.  Root-sheath. 

D.  Glassy  membrane. 

E.  Fibrous  wall  of  the  follicle. 

skin  and  terminates  in  a  bulb  usually  in  the  subcutaneous  tissue, 
where  it  rests  upon  a  papilla  composed  of  an  extremely  delicate 
pPexus  of  blood-capillaries. 

The  Hair-follicle. — The  root  of  the  hair,  in  its  passage  to  the 
papilla,  is  invested  with  sheaths  derived  from  the  skin.  The  hair, 
with  its  follicle,  is  indicated  in  transverse  section  in  Fig.  55.  A 
represents  the  medulla,  and  B  the  cortex  of  the  hair.  Outside  the 
root-sheath  C,  and  derived  from  the  rete  mucosum  of  the  epider- 
mis, is  a  thin  layer,  the  glassy  membrane  D.  This  is  projected 
from  the  basement  membrane  covering  the  surface  of  the  corium 


72  PRACTICAL    MICROSCOPY. 

or  true  skin.     The  whole  is  surrounded  by  a,  fibrous  coat  E,  derived 
from  the  connective  tissue  of  the  derma. 

A  vertical  section  of  the  follicle  is  indicated  in  Fig.  56.     A,  B, 
and  C  represent  the  epidermal  layers  which  do  not  enter  into  its 


FIG.  56.— DIAGRAM  SHOWING  MODE  OP  FORMATION  OF  HAIR-FOLLICLE. 
A'.    Epidermal  layers. 
B'.    Derma  or  true  skin. 

A.  Horny  layer  of  epidermis. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

The  three  last  mentioned  form  no  part  of  the  follicle. 

D.  Rete  Malpighii.    This  will  be  seen  projected  into  the  depths  of  the  true  skin  to  form 
the  root-sheath  G. 

E.  Hyaline  membrane  covering  the  derma.    This  is  projected  into  the  follicle,  forming 
the  glassy  membrane  H. 

F.  Fibrous  tissue  of  the  derma,  forming  the  fibrous  sheath  of  the  hair-follicle  I. 

G.  Root-sheath  of  the  hair-follicle. 
H.    Glassy  membrane  of  the  follicle. 
I.    Fibrous  sheath  of  the  follicle. 

J.    The  hair-follicle. 

composition.  The  rete  mucosum  D  forms  the  root-sheath  at  G. 
The  basement  membrane  of  the  corium  E  forms  the  glassy  mem- 
brane H,  while  the  connective  tissue  F  constitutes  the  fibrous  layer 
of  the  hair-follicle  J. 


SUDORIFEROUS   GLANDS. 

A  sweat-gland  consists  of  a  tube  or  duct  (vide  Fig.  57,  at  A) 
which,  from  the  opening  upon  the  surface,  passes  in  a  spiral  course 
through  the  several  layers  of  the  skin  to  the  deeper  part  of  the  co- 
rium, where  it  becomes  coiled  in  a  bun  oh  as  at  D.  The  coiled  or 
gland  part  of  the  tube  is  surrounded  by  a  network  of  capillaries. 
At  B,  the  tube  is  seen  in  transverse  section.  The  gland-tube  D  is 
provided  with  a  wall  of  connective  tissue  and  smooth  or  involuntary 
muscle,  lined  with  conical  cells.  The  epithelial  lining  of  the  duct 
C  is  granular;  the  lumen  small  and  lined  with  a  thin  cuticular 
membrane.  The  latter  constitutes  the  entire  wall  of  the  duct  as 


SUDORIFEROUS   AND   SEBACEOUS   GLANDS.  73 


FIG.  57.— SUDORIFEROUS  TUBULAR  GLAND. 

A.  Diagrammatic  sweat-gland.    C.    Its  duct.    D.    Coiled,  glandular  part. 

B.  The  same,  showing  a  transverse  section  of  both  parts.     X  400.    C'.    The  duct  lined 
with  several  layers  of  cells.    D'.    The  coiled  glandular  part  lined  with  columnar  cells  in  a 
single  layer. 


FIG.  58. — SINGLE  LOBULE  OP  A  SEBACEOUS  GLAND, 

A.  The  fibrous  wall  of  the  sac. 

B.  Involuntary  muscular  element  of  the  wall. 

C.  Polyhedral  cells  filling  the  sac  completely. 

D.  Fatty  degeneration  of  the  parenchyma  at  the  neck  of  the  gland,  formation  of  sebum, 
X400. 


74  PRACTICAL    MICROSCOPY. 

the  surface  of  the  epidermis  is  approached,  the  cellular  elements 
having  disappeared. 

Krause  estimated  the  number  of  sweat-glands  at  over  two  millions. 

SEBACEOUS    GLANDS. 

These  glands  are  little  sacs  or  lobules,  one  or  more  of  which 
open  into  each  hair-follicle.  These  sacs  are  entirely  filled  with' 
polyhedral  cells  (vide  Fig.  58).  At  the  neck  of  the  gland  the  cells- 
become  granular,  fatty,  and  disintegrated,  producing  the  sebum. 

MUSCLES    OF   THE    HAIR- FOLLICLES. 

Attached  to  the  fibrous  layer  of  each  hair- follicle  is  a  small 
'band  of  involuntary  or  smooth  muscular  fibre — the  arrector pill. 
This  passes  obliquely  toward  the  surface  of  the  skin;  and  when 
contraction  takes  place,  the  follicle  and  hair  are  elevated,  produc- 
ing the  phenomenon  known  as  goose-flesh. 

PRACTICAL  DEMONSTRATION. 

Remove  the  skin  from  the  parts  below  as  soon  after  death  as 
practicable.  Tissue  may  frequently  be  secured  after  surgical 
operations  from  stumps,  etc.  Dissect  deeply  so  as  to  preserve  the 
subcutaneous  tissue.  Small  cubes  from  the  finger-tips,  the  palm 
of  the  hand,  the  scalp,  and  the  groin  may  be  hardened  quickly  in 
strong  alcohol;  and  vertical  sections  should  be  made  as  soon  as  the 
tissue^  has  become  sufficiently  firm.  Stain  with  haema.  and  eosin, 
and  mount  in  dammar. 

The  structure  of  hairs  may  be  best  demonstrated  by  washing 
the  soap  from  lather,  after  shaving,  with  several  changes  of  water. 
AVhen  clean,  decant  the  water  and  add  alcohol.  After  twenty-four 
hours  again  decant  and  add  oil  of  cloves.  With  a  pipette  carry  a 
drop  of  the  oil  with  the  deposited  hair-cuttings  to  a  slide,  remove 
as  much  of  the  oil  as  possible  with  slips  of  blotting-paper,  and 
mount  in  dammar.  Oblique,  vertical,  and  transverse  sections  ma^r 
be  readily  obtained  by  this  method. 

VERTICAL  SECTION   OF   SKIN  FROM  THE  GROIN. 

(Vide  Fig.  59.) 
OBSERVE : 

(L.)* 

1.  The  horny  layer  of  the  epidermis.  (The  stratum  luci- 
dum  will  hardly  be  demonstrable  on  account  of  the  thinness  of  the 
epidermis  in  this  region.) 

*  Low  po\ver — i.e.,  from  thirty  to  sixty  diameters. 


VERTICAL    SECTION    OF    SKIN    FROM    THE    GROIN.  7.) 

2.  The  rete  mucosum.     (The  section  from  which  the  illus- 
tration has  been  drawn  was  taken  from  a  negro,  and  the  deep  cells- 
were  pigmented.) 

3.  The  sharp  line  of  demarcation  between  the  epidermis 
and  the  true  skin. 


FIG.  59.— VERTICAL  SECTION  OP  SKIN  FROM  THE  GROIN.    STAINED  WITH  H.EMA.  AND  EOSIN. 

A.  Epidermis. 

B.  Deep,  elongated  cells  of  the  rete  mucosum. 

C.  C.    Papillae  of  true  skin. 

D.  D.    Subcutaneous  areolar  tissue. 

E.  E.    Collections  of  adipose  tissue. 

F.  Shaft  of  hair  (obliquely  sectioned). 

G.  Root-sheath  of  last. 
H.    Fibrous  sheath  of  last. 

I.    Hair  papilla  (vertical  section). 

J,  J,  J.    Portions  of  sebaceous  glands  (one  on  the  extreme  right  of  the  cut  is  seen  in  con- 
nection with  the  hair-follicle). 
K,  K.    Arrectores  pili. 

L.    Hair-follicle  with  contained  shaft  of  hair  in  very  oblique  section. 
M,  M.    Coils  of  sudoriferous  glands. 
N.    Spiral  duct  of  last. 
O,  O.    Arteries  of  subcutaneous  plane. 

4.  The  papillae  of  the  corium  or  derma.     (Note  the  absence 
of  any  sharp  line  dividing  the  corium  and  subcutaneous  tissues.) 

5.  The  larger  blood-vessels  of  the  subcutaneous  region. 


76  PEACTICAL    MICROSCOPY. 

(The  arteries  in  transverse  section  are  plainly  indicated  by  their 
prominent  media,  the  appearance  of  the  fenestrated  membrane  as 
a  wavy  yellowish  line,  and  by  the  elliptical  or  circular  outline. 
The  veins  are  smaller,  with  thinner  walls,  and  their  outline  is  gen- 
erally irregular.  The  smaller  veins  are  commonly  overlooked,  on 
account  of  their  lumen  having  become  obliterated  by  contraction 
of  the  tissue  in  hardening.) 

6.  Coils  and  ducts  of  sweat-glands  in  last   region.     (The 
tubes  are  cut  in  various  directions,  and  the  whole  is  surrounded  by 
dense  fibrous  tissue,  forming  a  kind  of  capsule.) 

7.  The  collections  of  adipose  tissue  beneath  the  last  region. 
(The  septa  are  dense  and  strong.) 

8.  (Having  selected  a  vertical   section  of  a  hair-follicle:)   (a) 
The  root  of  the  contained   hair,     (b)  The  bulb  and  the  hair 
papilla,     (c)  The  medulla  of  the  hair,     (d)  The  root-sheath 
prolonged  from  the  rete  mucosum.  (e)  The  fibrous  (outer)  sheath. 

9.  The  sebaceous  glands.     (The  demonstration  of  the  con- 
nection between  the  neck  of  the  gland  and  the  follicle  will  require 
a  very  favorable  section.) 

10.  (Scattered  through   the  corium  and   upper  subcutaneous 
region:)  (a)  Small  portions  of  sebaceous  glands,     (b)  Ducts 
of  sudoriferous  glands,    (c)  Oblique  sections  at  various  angles 
of  hair-follicles,    (d)  Small  vessels. 

11.  Arrector  pili  muscle.     (Nearly  always  to  be  found  stand- 
ing obliquely  to  the  divided  hair-follicle.) 

<H.)* 

12.  (If  demonstrable :)  (a]  The  stratum  lucidum.     (b)  Stra- 
tum granulosum. 

13.  The  elongate  cells  of  the  rete,  next  the  corium. 

14.  (Where  the  tissue  has  been  torn :)  The  impacted  cells  of 
the  horny  epidermis. 

15.  The  basement  membrane  covering  the  corium. 

16.  Capillaries  of  the  papillae  of  the  corium.     (These  may 
be  distinguished,  when  seen  longitudinally,  by  tortuous  lines  of 
elongate  and  deeply- stained  nuclei  belonging  to  the  endothelium. 
Arterioles  may  be  differentiated  by  their  long  muscle  cells,  the  cir- 
cular fibres  lying  transversely  to  the  vessel.) 

17.  The  root-sheath  of  the  hair-follicles.     (The  cells  com- 
posing the  root-sheath  vary  in  appearance,  according  to  their  posi- 

*  High  power — i.e.,  from  three  to  four  hundred  diameters. 


VERTICAL   SECTION   OF   SKIN   FROM   THE   GROIN.          77 

tion  relatively  to  the  hair;  and  this  will  enable  you  to  demonstrate 
two  layers,  or  an  inner  and  an  outer  root-sheath.) 

18.  The  glassy  membrane  of  the  hair-follicle.    (Appearing 
simply  as  a  clear  space  between  the  root-sheaths  and   the  outer 
fibrous  coat.) 

19.  The  intra-cellular  network  in  the  large  polyhedral  cells 
of  the  sebaceous  glands,  and  the  minute  fat-globules  in  the  same. 

20.  The  nuclei  of  the  fat-cells  in  the  adipose  tissue.     (They 
appear  pressed  to  one  side.) 

21.  Medullated  nerve  bundles  in  transverse  or  oblique  sec- 
tion. 


78  PRACTICAL    MICROSCOPY. 


THE  TEETH. 

A  human  dentinal  tooth  is  a  calcific  structure  of  extreme  hard- 
ness, and  is  divided  into  an  exposed  crown,  a  constricted  neck,  and 
one  or  more  concealed  fangs — the  latter  being  inserted  into  an 
alveolus,  by  means  of  which  the  whole  is  firmly  connected  with  the 
maxilla. 

The  central  portion  presents  an  elongate  cavity  (pulp- chamber) 
containing  vascular,  nervous,  and  connective-tissue  elements — the 
pulp. 

The  pulp-cavity  is  surrounded  by  the  dentine,  which  constitutes 
the  major  portion  of  the  tooth. 

The  crown  portion  of  the  dentine  is  provided  with  a  covering 
of  enamel,  while  the  fang  is  invested  with  an  osseous  cement,  the 
crusta  petrosa. 

A  thin  (one-twenty-five-thousandth  to  one-fifty-thousandth  of  an 
inch)  membrane — the  cuticula — covers  the  enamel  in  early  life, 
while  the  crusta  receives  a  periosteal  investiture.  The  vascular  and 
nervous  elements  of  the  pulp  obtain  admission  to  the  pulp-cavity 
by  a  perforation  or  foramen  at  the  apex  of  the  fang,  the  foramen 
dentium. 

The  Pulp. — The  ground-substance,  or  stroma  of  the  pulp,  is  a 
form  of  primitive  connective  tissue,  gelatinous  rather  than  mark- 
edly fibrous.  It  contains  elongate  capillary  loops,  multipolar  cells, 
medullated  and  non-medullated  terminal  nerve  fibrils. 

Surrounding  the  pulp  mass,  and  next  to  the  dentinal  wall  of 
the  chamber,  we  find  a  single  layer  of  elongate  cells — odontoblasts. 
These  are  in  communication,  by  means  of  processes,  or  prolonga- 
tions, with  fibrous  elements  of  the  pulp. 

Dentine. — The  dentinal  stroma  or  matrix  is  cartilaginous,  with 
calcific  elements,  and  is,  next  to  the  enamel,  the  hardest  tissue  of 
the  body.  The  matrix  is  pierced  with  the  dentinal  canals  (one-ten- 
thousandth  to  one-twenty-thousandth  of  an  inch  in  diameter), 
which  radiate  from  their  beginning,  next  the  pulp-chamber,  toward 
the  outer  portion  of  the  dentine.  These  canals  branch  and  anasto- 
mose, and  are  lined  with  an  exceedingly  thin  dentinal  sheath. 

From  the  outer  extremity  of  the  odontoblasts  of  the  pulp  nu- 
merous prolongations  are  sent  which  are  continued  within  the  den- 
tinal canals  as  the  dentinal  fibres.  The  dentinal  canals  terminate 
exteriorly,  by  very  fine  lumina,  in  a  system  of  irregularly-formed 
openings,  interglobular  spaces,  which  are  channelled  in  the  outer 


THE   TEETH. 


79 


part  of  the  dentine.     The  dentinal  terminal  fibres  are  in  connec- 
tion with  branched  cells  which  occupy  the  interglobular  spaces. 


FIG.  60.— VERTICAL  SECTION  OF  BICUSPID  TOOTH.    DIAGRAMMATIC. 

A,  A.    Pulp-chamber. 

B,  Foramen  dentium  for  entrance  of  vascular  and  nervous  elements  to  the  pulp. 

C,  C,  C.    Dentine.    The  lines  point  to  the  incremental  lines  of  Salter,  imperfectly  calcified 
dentinal  stroma. 

D,  D.    Interglobular  spaces  in  last  layer,  forming  the  granular  layer  of  Purkinje. 

E,  E.    Crusta  petrosa  or  cement  substance. 

F,  Enamel.    The  parallel  lines  are  intended  to  indicate  the  stripes  of  Ketzius  due  to  the 
formation  of  the  enamel  in  successive  layers. 

G,  The  cuticula. 

The  Enamel. — The  part  of  the  dentine  above  the  neck  of  the 
tooth  is  protected  by  a  covering  of  enamel.  The  enamel  consists 
of  prisms  from  one-six-thousandth  to  one-eight-thousandth  of  an 


80  PRACTICAL    MICROSCOPY. 

inch  in  diameter  which  pass  in  a  direction  nearly  at  right  angles  to 
the  surface  of  the  dentine.  They  are  of  extreme  density,  contain 
little  besides  inorganic  material,  and  in  a  vertical  section  the  whole 
is  traversed  by  parallel  striae,  not  unlike  the  markings  indicating 
tree-growth — the  lines  of  Retzius. 

Crusta  Petrosa. — The  fang  portion  of  the  dentine  is  invested 
with  a  thin  layer  of  true  bone,  arranged  in  laminae-  and  containing 
lacuna  and  canaliculi,  but  no  Haversian  canals.  The  crusta  is 
provided  with  periosteum,  which  forms  the  bond  of  union  between 
the  teeth  and  the  process  of  the  maxillae.  The  lacunar  bone  cor- 
puscles are  in  connection,  through  the  canaliculi,  with  the  cells  in 
the  interglobular  spaces  of  the  dentine.  It  will  be  seen  that  the 
connective-tissue  elements,  at  least  of  the  pulp,  are  in  eventual 
histological  connection  with  the  bone  corpuscles  of  the  crusta. 

PRACTICAL   DEMONSTRATION. 

The  illustrations  common  to  our  text-books  have  been  drawn 
from  dried  teeth,  ground  down  to  the  requisite  thinness  by  means, 
of  corundum  or  emery  wheels.  This  is  a  very  tedious  process,  and 
is  impracticable  with  the  student.  If  such  specimens  are  desired 
it  will  be  advisable  to  purchase  them  already  mounted.  They  only 
give  the  skeleton  of  the  organ,  all  the  soft  tissues  being  destroyed 
by  the  drying  and  grinding. 

While  dry  specimens  exhibit  the  plan  of  a  tooth,  the  soft  tissues 
must  be  studied  in  sections  made  after  the  inorganic  constituents 
have  been  removed.  Teeth  immediately  after  extraction  are  to  be 
treated  in  the  same  manner  as  described  for  bone.  A  one-sixth 
per  cent  of  chromic-acid  solution,  to  which  five  drops  of  nitric  or 
hydrochloric  acid  have  been  added,  may  be  first  used.  Let  the 
quantity  of  liquid  be  liberal,  and  from  time  to  time,  say  every 
three  days,  add  a  few  drops  of  the  nitric  acid.  The  decalcification 
should  proceed  slowly  and  may  be  complete  in  from  two  to  three 
or  four  weeks.  The  earthy  matters  will  first  be  dissolved  from  the 
surface.  Watch  the  action  carefully,  ascertaining  the  progress  of 
decalcification  by  pricking  a  fang  with  the  needle.  If  the  acid  be 
too  strong,  and  the  action  too  rapid,  the  whole  may  be  destroyed. 
When  the  decalcification  is  complete,  a  needle  may  be  easily  passed 
through  the  tooth  and  sections  be  made  with  the  razor  or  knife,, 
with  or  without  a  microtome.  The  form  will  be  preserved  except 
as  regards  the  enamel ;  this  will  be  entirely  dissolved.  The  en- 
amel prisms  may  be  demonstrated  by  treating  broken  fragments, 
with  dilute  acid  for  a  short  time  only. 

Sections  should  be  stained  with  carmine  and  picric  acid  and 
mounted  in  glycerin.  For  the  study  of  the  development  of  teeth, 
foetal  jaws  may  be  treated  as  just  described;  and,  when  properly 
decalcified  and  hardened,  should  be  infiltrated  with  celloidin,  sec- 
tioned, and  stained.  I  would  refer  the  student  to  the  excellent 
article  on  the  subject  in  Dr.  C.  Heitzmann's  "  Morphology/' 


TEETH. — PRACTICAL    DEMONSTRATION.  81 

TKANSVEKSE  SECTION   OF  FANG   OF   HUMAN  DECID- 
UOUS CANINE   TOOTH.— DECALCIFIED. 

(Fig.  61.) 
OBSERVE  : 

(L.) 

1.  Division  into  pulp,  dentine,  crusta  petrosa,  and  peri- 
osteum. 

2.  Line  of  junction  of  pulp  and  dentine.     (If  the  elements 
of  the  pulp  are  intact,  note  the  layer  of  deeply-stained  odonto- 
blasts  next  the  dentine.) 


FIG.  61.— TRANSVERSE  SECTION  OF  FANG  OF  A  DECIDUOUS  CANINE  TOOTH,  DECALCIFIED  WITH 
CHROMIC  AND  NITRIC  ACIDS  AND  STAINED  WITH  PICRO-CARMINE. 

A,  B.  Line  through  the  dentine  indicating  the  point  at  which  the  edges  have  been  made 
to  join  after  the  omission  of  an  intervening  portion.  This  was  necessary  in  order  that  the 
different  layers  might  be  shown  in  a  single  drawing. 

C,  D.    Junction  line  between  the  pulp  and  dentine. 

E,  F.    Junction  line  between  dentine  and  crusta  petrosa. 

G,  G.    Odontoblasts  of  the  pulp. 

H,  H.    Stellate  connective-tissue  cells  of  the  pulp. 

I,  I.    Dentinal  processes  of  odontoblasts. 

J,  J.    Dentinal  fibres. 

K,  K.    Terminal  branching  dentinal  fibres. 

L,  L.    Interglobular  spaces  of  dentine. 

M,  M.    Lacunae  of  the  crusta  petrosa.    The  drawing  does  not  show  the  periosteal  invest^ 
ture  of  the  crusta.     X  400. 
0 


82  PEACTICAL    MICROSCOPY. 

3.  External  limit  of  dentine.     (Note  here  the  deeply-stained 
granular  line  of  Purkinje.     This  is  the  location  of  the  interglob- 
ular  spaces.     The  deep  color  is  due  to  the  staining  of  their  cell 
contents.) 

4.  The  striae  of  the  dentine  (dentinal  canals  and  stained  con- 
tents). 

5.  The  laminated  crusta.     (The  yellowish-pink  dots  on  the 
lacunae.) 

(H.) 

6.  Elements  of  the  pulp,     (a)  The  layer  of  odontoblasts 
(note  their  internal  processes  connecting  with  other  cells  of  the 
pulp;    and  the  external  processes  passing  into  the  dentinal 
canals),     (b)  The  sparsely  fibrillated  character  of  the  pulp 
tissue,     (c)  Sections  of  vascular  loops.     (The  nerve  elements 
may  be  demonstrated,  particularly  if  the  section  be  made  near  the 
apex  of  the  fang,  where  the  fibres  are  medullated.     The  terminal 
fibrillse  are  non-medullated.) 

7.  Dentinal  elements,     (a)  The  dentinal  canals,     (b)  The 
dentinal  sheath.     (Better  demonstrated  in  'transverse  sections.) 
{c)  Dentinal  fibres.     (In  transverse  sections  the  canals  are  well 
shown  lined  with  a  membrane  of  extraordinary  tenuity,  with  the 
fibre  appearing  as  a  central  dot.)     (d)  Fine  dentinal  fibres  near 
the  outer  limit,     (e)  Interglobular  spaces.     (An  occasional  cell 
may  be  made  out  in  the  larger  spaces.     They  were  formerly  sup- 
posed to  contain  a  gelatinous  material  only.     Note  the  connection 
between  these  spaces  and  the  termini  of  the  dentinal  fibres.) 

8.  The  Crusta  Petrosa.     (a)  Its  laminated  formation,     (b) 
The  lacunae,     (c)  Bone  corpuscles  in  the  last.     (The  canali- 
culi  are  not  well  demonstrated  here,  as  the  tissue  is  very  translucent 
and  feebly  stained.     These  minute  canals  are  better  indicated  in 
dried  bone.) 

9.  The  periosteum.     (Note  its  dense  fibrillar  meshwork.) 


THE   STOMACH.  83 


THE   STOMACH  AKD   INTESTINES. 

The  stomach  and  intestines  are  lined  with  mucous  membrane, 
i.e.,  a  membrane  containing  glands  which  secrete  mucus. 

The  gastric  and  intestinal  mucous  membranes  are  constructed 
as  follows : 

1.  The  epithelial  lining. 

2.  The  mucosa. 

3.  The  muscularis  mucosce. 

4.  The  submucosa. 

5.  The  muscular  walls  proper. 

6.  The  fibrous  or  peritoneal  investment. 

In  descriptive  anatomy,  the  first  four  of  the  above  are  included 
in  the  mucous  coat. 

The  epithelium  of  the  inner  surface  of  that  portion  of  the  ali- 
mentary tract  under  consideration  is  of  the  columnar  variety.  Varia- 
tions occur  in  the  deeper  layers,  which  will  be  referred  to  later  on. 

The  mucosa,  with  its  epithelial  covering,  is  thrown  into  coarse 
folds,  rugce  or  valve-like  reduplications,  which  greatly  increase  the 
extent  of  surface.  It  contains  the  principal  glands  and  capillary 
blood-vessels.* 

The  muscularis  mucosse  is  a  thin  layer  of  involuntary  muscular 
fibre  which  separates,  the  mucosa  from  the  submucosa. 

The  submucosa,  composed  of  loose  areolar  tissue,  serves  to  con- 
nect the  previous  structures  with  the  muscular  coat  proper,  and 
contains  the  larger  trunks  from  which  the  capillaries  of  the  mucosa 
either  take  their  origin,  or  into  which  they  empty.  An  intricate 
plexus  of  lymphatics  is  also  here  situated. 

The  muscular  coat  consists  of  strong  bands,  running  in  two  or 
three  directions.  The  muscle  plates  are  sustained  by  connective 
tissue. 

A  peritoneal  investment  covers  the  organs,  except  at  such  points 
as  are  occupied  by  the  entrance  and  exit  of  blood-vessels,  etc. 

THE   STOMACH. 

The  mucosa  everywhere  contains  microscopical  depressions,  the 
gastric  tubules  or  peptic  glands.  These  are  concerned  in  the  pro- 
duction of  the  gastric  juice,  and  in  the  absorption  of  fluids. 

*  It  is  not  always  possible  in  mucous  membranes  to  differentiate 
clearly  between  an  epithelial  lining  and  the  mucosa;  and  in  the  stom- 
ach and  intestine  thev  may  be  both  included  in  the  mucosa. 


84 


PRACTICAL    MICROSCOPY. 


The  several  layers  of  the  stomach  may  be  better  understood  by 
reference  to  the  diagram  (Fig.  62). 

The  gastric  tubular  glands  are  of  two  principal  varieties,  viz. : 

1,  the  peptic  glands,  found  in  the  cardiac  portion  of  the  stomach; 

2,  the  pyloric  glands,  which  occupy  the  pyloric  extremity  of  the 
organ.     The  mucous  membrane,  midway  between  the  cardiac  and 
pyloric  portions,  is  occupied  by  tubules  which  partake  of  the  char- 
acter of  both  peptic  and  pyloric  glands,  so  that  no  sharp  boundary 
line  exists. 

The  peptic  or  cardiac  gland-tubes  penetrate  to  the  muscularis 


FIG.  62.— DIAGRAM  OP  THE  WALL  OF  THE  STOMACH  IN  VERTICAL  SECTION. 

A.  Layer  of  gastric  tubules. 

B.  Vascular  portion  of  mucosa. 

C.  Muscularis  mucosse. 

D.  Submucosa. 

E.  Internal  circular  layer  of  muscular  fibre. 

F.  External  oblique  and  ongitudinal  muscular  layers. 

G.  Peritoneum. 

I,  I,  I.    Lumen  of  gastric  tubules. 
J,  J.    Branching  gastric  tubules. 

K,  K.    Blood-vessels  arising  from  lower  portion  of  mucosa,  forming  plexus  between  the 
tubules. 

mucosae.  They  pursue  a  somewhat  wavy  course,  and  at  their  lower 
or  blind  extremity  are  frequently  bifid.  They  are  lined  at  their 
commencement  on  the  surface  with  translucent  columnar  epithe- 
lium, the  cells  being  polygonal  in  transverse  section.  As  the 
fundus  or  bottom  of  the  tube  is  approached,  the  lining  cells  become 


THE    STOMACH.  85 

granular,  larger,  and  somewhat  polyhedral.  Next  the  wall  of  the 
tube,  large,  granular,  bulging  cells  are  scattered  irregularly.  The 
epithelium  occupies  the  major  portion  of  the  space  in  the  tube,  so 
that  the  lumen  is  very  small. 

A  single  bifid  tube  is  represented  in  Fig.  63.  The  prominent 
distinguishing  feature  of  the  peptic  or  cardiac  tubules  is  afforded 
by  the  large  border  or  parietal  cells.  The  cells  next  the  lumina  are 
called  central  or  chief  cells. 

The  pyloric  gland-tubes  pursue  a  course  not  greatly  unlike  that 
of  the  tubes  just  mentioned.  They  do  not  branch,  however,  until 
they  have  penetrated  well  down  toward  the  muscularis  mucosae. 


FIG.  63.— VERTICAL  SECTION  OF  A  PEPTIC  TUBULA.R  GLAND,  FROM  CARDIAC  MUCOSA  OF  STOM- 
ACH.  LARGELY  DIAGRAMMATIC. 

A.  Lumen  of  duct  portion  of  tubule. 

B.  Neck  of  last. 

C.  Gland  portion. 

D.  D.    Central  cells. 

E.  E.    Border  cells. 

F.  The  glandular  portion  in  T.  S. 

G.  Line  of  commencing  muscularis  mucosae. 

Their  distinguishing  character  is  afforded  by  the  epithelial  lining. 
At  the  surface,  the  cells  are  columnar  with  polygonal  transection. 
The  deeper  parts  are  lined  with  translucent  cylinders.  The  lumina 
are  larger  than  those  of  the  peptic  tubes. 

The  gastric  gland-tubes  are  placed  thickly  side  by  side,  their 
bases  reaching  the  muscularis  mucosae.  Between  and  beneath  the 
tubes  is  a  dense  network  of  blood  capillaries. 

The  remainder  of  the  stomach  has  little  special  interest  for  the 


PRACTICAL    MICROSCOPY. 


histologist.  The  muscular  portion  of  its  walls  consists  of  a  thin 
internal  circular  layer,  with  oblique  bundles  interspersed,  and  a 
thin  external  longitudinal  layer  of  the  involuntary  variety.  Be- 
tween the  two  layers  is  found  a  plexus  of  non-medullated  nerves, 


FIG.  64.— VERTICAL,  SECTION  OF  TORTUOUS  AND  BRANCHING  TUBULAR  GLAND,  FROM  PYLORIC 
MUCOSA  OF  STOMACH.    DIAGRAMMATIC. 

A.  Lumen.    This  is  often  much  widened. 

B.  Duct  portion  of  tubule. 

C.  Branching  glandular  portion. 

D.  Transverse  section  of  the  last. 

E.  Lower  limit  of  mucosa. 

corresponding  to  the  plexus  of  Auerbach  of  the  intestines,  but 
which  is  not  demonstrable  by  ordinary  methods  or  sections. 

The  blood-supply  is  received  at  the  curvatures.  Branches  pene- 
trate the  muscular  layers  along  the  lines  of  omental  attachment,  as 
blood-vessels  never  penetrate  the  peritoneum. 

The  peritoneum  is  constructed  mainly  of  fibrous  tissue,  with  an 
external  investment  of  pavement  epithelium. 

PRACTICAL  DEMONSTRATION. 

Inasmuch  as  the  human  stomach  cannot  often  be  obtained  until 
decomposition  has  destroyed  it  for  our  work,  we  must  secure  the 
organ  from  some  one  of  the  lower  animals.  The  stomach  of  the 
dog  presents  all  the  histological  features  of  that  of  man,  and  can 
be  gotten  in*  good  condition  from  an  animal  recently  killed. 

Harden  small  pieces  in  strong  alcohol,  and  cut  sections  at  right 
angles  to  the  surface  and  from  different  regions.  Stain  with  haema. 
and  eosin,  and  mount  in  dammar. 


STOMACH. — PRACTICAL   DEMONSTRATION. 


87 


VERTICAL   SECTION    FROM    GREATER   CURVATURE 
OF   DOG'S   STOMACH. 

(Fig.  65.) 
OBSERVE: 
(L.) 

1.  The  division  into:  (a)  Surface  epithelium   (free  ends  of 
gland-tubes),    (b)  Mucosa.    (c)  Muscularis  mucosae.     (d)  Sub- 


FIG.  65.— VERTICAL  SECTION  OF  WALL,  OF  CENTRAL  PORTION  OF  DOG'S  STOMACH. 
A.    Internal  surface,  showing  open  mouths  of  the  gastric  tubules,  lined  with  clear  colum- 


nar cells. 

B.    Deepest  portion  of  submucosa. 
D.    Submucosa. 
F.    Bundles  of  muscular  tissue  (internal  circular). 


C.    Muscularis  mucosae. 
E.    Adipose  tissue  in  last. 
X60. 


mucosa.      (e)  Muscular  layers.      (Only  a  portion  of  the  inner 
circular  layer  is  shown.     It  has  been  divided  transversely.) 

(H.) 

2.  The  epithelium  of  gland-tubes.  (The  upper  portion  of 
the  tubes  will  be  cut  obliquely  in  many  places,  as  they  have  been 
inclined,  and  the  epithelium  will  show  as  a  beautiful  mosaic  of 
polygonal  areas.)  (a)  The  differentiation  between  border  and 


88  PRACTICAL    MICROSCOPY. 

central  cells,  (b)  Tubes  cut  transversely,  showing  the 
lumina.  (c)  Indications  of  the  capillary  plexuses  between  the 
tubes. 

3.  The  mucosa.     (a)  Arterioles  and  venules  beneath  the 
tubules,    (b)  Scattered  lymphoid  cells  (round  cells  with  one,  two, 
or  three  nuclei). 

4.  The  muscularis  mucosae.     (Note  the  elongated  nuclei  of 
the  smooth  muscle  cells.) 

5.  The  submucosa.     (a)   Arteries,  veins,  etc.,  cut  in  vari- 
ous directions,     (b)  The  adipose  tissue.     (Crystals  of  the  fatty 
acids  are  frequently  seen  in  the  cells  when  freshly  mounted.) 

6.  The  muscular  bundles  of  the  circular  layer  with  the 
septa  of  connective  tissue.     (Note  particularly  the  various  ap- 
pearances presented  by  bundles  of  involuntary  muscular  fibre  when 
cut  in  different  planes.) 

SMALL  INTESTINE. 

The  histology  of  the  intestine,  both  large  and  small,  is  formed 
upon  the  general  plan  of  that  of  the  stomach.  The  same  layers 
are  presented :  the  mucosa,  with  its  epithelial  covering ;  the  muscu- 
laris mucosce;  the  submucosa;  the  muscular  and  the  peritoneal 
coats. 

The  mucosa  of  the  small  intestine  is  everywhere  pierced  by 
blind  depressions;  or,  what  is  equivalent,  the  surface  is  studded 
with  minute  elevations  or  papillae,  between  which  are  the  depres- 
sions which  correspond  to  the  tubules  of  the  stomach.  The  eleva- 
tions are  called  villi,  the  depressions  between  the  villi,  crypts. 

The  small  intestine  serves  two  important  functions:  1.  The 
secretion  of  a  fluid,  one  of  the  digestive  juices — the  succus  enteri- 
cus.  2.  The  absorption  of  food,  especially  the  fats  or  hydrocar- 
bons. 

We  shall  view  the  histology  of  this  organ  from  a  physiological 
standpoint,  considering:  1st,  Those  structures  concerned  in  the 
secretion  of  the  succus  entericus;  2d,  Those  portions  concerned  in 
absorption  of  food. 

HISTOLOGY    OF   THOSE   PARTS   OF   THE    SMALL   INTESTINE    PARTICU- 
LARLY  CONCERNED    IN   THE    PRODUCTION   OF   THE 
SUCCUS   ENTERICUS. 

The  diagram  (Fig.  66)  is  intended  to  represent  at  A  the  thick- 
ness of  the  mucosa  with  its  papillary  elevations — the  villi.  The 


THE   SMALL   INTESTINE. 


89 


muscularis  mucosae  B,  from  which  the  villi  arise,  separates  the 
mucosa  from  the  submucosa  C.  The  horizontal  line  at  the  bottom 
of  the  diagram  indicates  the  outer  limit  of  0  and  the  beginning  of 
the  circular  muscular  coat  of  the  intestine.  The  villi,  everywhere 
covered  with  columnar  epithelium,  are  represented  in  the  drawing 
as  widely  separated,  but  in  the  gut  they  are  so  closely  studded  as 
to  afford  but  narrow  chinks  (crypts)  between  the  prominences. 
In  the  interior  of  each  villus  is  a  fine  network  of  blood  capillaries 
(G  G).  The  cells  on  the  borders  of  the  villi  secrete  certain  fluid 
material  from  the  blood  circulating  in  the  capillary  plexuses,  and 
pour  it  out  into  the  crypts.  The  crypts  becoming  filled  with  the 
fluid,  the  latter  overflows  and  passes  into  the  lumen  of  the  gut,  to 
act  in  promoting  digestion.  This  is  one  source  of  the  succus  en- 
tericus,  and  there  is  yet  another. 


D- 


TIG. 


3. — DIAGRAM  SHOWING  PORTIONS  OF  INTESTINAL  Mucous  MEMBRANE,  CONCERNED  IN 
THE  SECRETION  OF  THE  Succus  ENTERICUS. 

A.  The  mucosa. 

B.  Muscularis  mucosse. 

C.  Submucosa. 

D.  D,  D.    Villi. 

E.  F.    Crypts  of  Lieberkuhn. 

0,  G,  G.    Blood  plexuses  of  villi. 

H,  H.    Large  vessels  of  submucosa,  supplying  the  epithelium  covering  the  villi. 

1.  Neck  of  a  gland  of  Brunner. 

J,  J,  J.    Gland  of  Brunner  in  the  submucosa.    The  secretion  is  emptied  into  the  crypts  as 
atF. 

From  the  bottom  of  some  of  the  crypts,  tubes  will  be  found 
which,  piercing  the  muscularis  mucosre,  reach  the  submucosa,  where 
they  branch,  become  convoluted,  are  lined  with  secreting  cells,  and 
are  known  as  the  glands  of  Brunner.  These  glands,  which  are 
practically  elongated  crypts,  are  surrounded  by  blood  capillaries, 
and  the  gland-cells  secrete  a  fluid  which  is  poured  into  the  gut  at 


90 


PRACTICAL    MICROSCOPY. 


the  base  of  the  crypts,  when  it  becomes  mingled  with  the  secretion 
previously  mentioned,  and  constitutes  the  succus  entericus. 

We  have,  then,  seen  that  the  succus  entericus  is  secreted,  partly 
from  the  epithelial  cells  covering  the  villi  (or,  in  other  words,  sur- 
rounding the  crypts)  and  partly  from  the  cells  of  B  runner's  gland*. 


THE    REMAINING    STRUCTURES    OF    THE    INTESTINE    CONCERNED 
MAINLY    IN    FOOD    ABSORPTION. 

The  diagram  (Fig.  67)  is  intended  to  show  the  same  layers  as 
were  indicated  in  the  previous  figure  (Brunner's  glands  and  the 
blood-vessels  have  been  omitted  in  order  to  avoid  confusion).  The 
villi  and  crypts  are  seen  as  before. 


FIG.  67. — DIAGRAM  SHOWING  PORTIONS  OF  INTESTINAL  Mucous  MEMBRANE,  CONCERNED  IN 

"  ABSORPTION. 

A.  Mucosa. 

B.  Muscularis  mucosae. 

C.  Submucosa. 

D.  D.    Villi. 

E.  F.    Crypts  of  Lieberkuhn. 
G,  G.    Lacteals. 

H,  H.    Chinks  and  intercommunicating  channels  of  the  lymph  plexus  of  the  submucosa. 
I.    Bottom  of  a  mass  of  adenoid  tissue— a  so-called  solitary  gland.    Peyer's  patches  are 
formed  of  aggregations  of  these  nodules. 
J.    Efferent  lacteal  or  lymph  duct. 

In  the  centre  of  each  villus  is  the  blind  tube  G  G,  a  part  of  the 
lymphatic  system,  and  here  called  a  lacteal.  When,  during  diges- 
tion, the  minute  globules  of  fatty  food  reach  the  small  intestine, 
they  are  grasped  by  the  epithelial  cells  covering  the  villi,  and  are 
carried  eventually  within  the  body  of  the  villus  to  this  lacteal. 


THE   INTESTINES.  91 

The  lacteals  pierce  the  muscularis  mucosae,  and  in  the  submu- 
cosa  are  in  connection  with  a  plexus  of  lymphatic  tubes  and  spaces. 
They  eventually  unite  with  efferent  lymph-tubes  (J),  and  pass  by 
menus  of  the  mesentery  to  the  receptaculum  chyli. 

Connected  with  the  plexus  of  lymphatics  in  the  submucosa  are 
minute  nodules  of  lymphoid  structure  (adenoid  tissue),  which  have 
unfortunately  been  called  lymphatic  glands.  They  are  in  no  sense 
glands. 

Slit  up  a  portion  of  intestine  along  the  attached  border,  and 
carefully  examine  the  inner  surface :  it  will  present  a  velvety  ap- 
pearance, due  to  the  minute  villi.  You  will  also  find  little  nodules, 
perhaps  one-sixteenth  of  an  inch  in  diameter,  scattered  here  and 
there  in  the  mucous  coat.  These  are  the  lymphatic  nodules  al- 
luded to  above — the  so-called  solitary  glands.  One  of  the  nodules 
is  indicated  in  the  diagram  at  I,  with  its  point  projecting  into  the 
crypt  F. 

Continuing  your  examination  of  the  gut,  you  will  discover,  es- 
pecially in  the  ileum,  roughened  patches  perhaps  two  inches  long 
by  half  an  inch  broad.  These  are  collections  of  the  lymphatic 
nodules  described  in  the  last  paragraph,  and  are  termed  agminate 
glands  or  patches  of  Peyer.  They  have  no  secretive  power,  being 
simply  in  connection  with,  and  a  part  of,  the  chain  of  lymphatics 
in  the  walls  of  the  intestine.  They  consist  of  adenoid  tissue,  which 
will  be  described  with  the  lymphatics. 

To  recapitulate,  the  small  intestine  presents  the  following: 

1.  The  villi,  each  containing  a  plexus  of  blood-capillaries  and 
the  lymphatic  or  absorbent  vessel. 

2.  Crypts  or  follicles  of  LieberJcuhn,  which  are  simply  depres- 
sions between  the  villi. 

3.  Brunner's  glands,  the  only  true  glands  of  the  gut,  unless  the 
crypts  are  so  classified. 

4.  Solitary  lymphatic  nodules,  the  so-called  solitary  glands. 

5.  Agminate  lymphatic  nodes,  agminate  glands  or  patches  of 
Peyer,  consisting  of  aggregations  of  solitary  lymphatic  nodules. 

The  muscular  part  of  the  intestine  is  arranged  not  unlike  that 
portion  of  the  stomach,  i.e.,  with  an  inner  circular  and  an  outer 
longitudinal  layer.  Between  the  two  is  located  Auerbach's  plexus 
of  non-medullated  nerves.  A  similar  plexus,  Meissner's,  is  found 
in  the  submucosa.  These  we  shall  not  attempt  to  demonstrate. 

A  small  quantity  of  areolar  tissue  connects  the  external  longi- 
tudinal muscular  layer  with  the  peritoneal  investment. 


PRACTICAL    MICROSCOPY. 


PRACTICAL   DEMONSTRATION. 

The  intestines  of  the  dog  or  rabbit  are  more  commonly  used  for 
practical  work,  for  reasons  already  alluded  to.  The  tissue  should 
be  cut  in  small  pieces,  and  hardened  quickly  in  alcohol.  When 
human  intestine  can  be  obtained  fresh,  a  piece,  say  three  inches 
long,  should  be  emptied  of  its  contents,  filled  with  alcohol  by  tying 
the  ends,  and  the  whole  hardened  in  strong  spirit.  Under  no  cir- 
cumstances should  the  gut  be  washed,  and  great  care  must  be  taken 
to  avoid  injuring  the  delicate  cells  covering  the  villi.  Vertical  sec- 
tions with  the  microtome  are  the  most  valuable.  Stain  with 
haema.  and  eosin3  and  mount  permanently  in  dammar. 

VERTICAL  SECTION  OF  THE  ILEUM,  INCLUDING  POR- 
TION  OF   A   PATCH   OF   PEYER.     HUMAN. 

1  Vide  Fig.  68.) 
OBSERVE: 

(W 

1.  The  villi.     (a)  That    they  are  of  varying    lengths, 
slender,  wavy,  and  delicate,     (b)  The  covering  of  columnar 


FIG.  68.— INTESTINAL  Mucous  MEMBRANE  THROUGH  A  PEYER'S  PATCH,  VERTICAL  SECTION. 
Stained  with  Haema.  and  Eosin.     X  250. 

A,  A,  A.    Villi. 

B.  Transverse  sections  of  crypts  of  Lieberkiihn. 

C,  C.    Crypts  in  vertical  section. 

D,  D,  D.    Nodules  of  lymphoid  tissue— constituting  a  patch  of  Peyer. 

E.  Muscularis  mucosae. 

F.  Submucosa. 


THE   ILEUM. — PRACTICAL   DEMONSTKATI 

cells.  (The  free  extremities  of  many  of  the  villi  in  the  drawing 
are  seen  broken,  and  the  epithelium  is  wanting  in  places.  It  is 
almost  impossible  to  secure  perfect  villi  from  human  intestine, 
on  account  of  the  length  of  time  usually  intervening  between  death 
and  the  removal  of  the  tissue.)  (c)  Oblique  sections. 

2.  The  crypts  of  Lieberkuhn. 

3.  The  lymphatic  nodules  (so-called  solitary  glands),  consti- 
tuting the  elements  of  a  patch  of  Peyer.     (a)  Their  projection 
upon  the  mucous  surface  of  the  gut  between  the  villi.    (b} 
The  covering  with  epithelium  on  their  free  borders.     (They 
are  located,  properly  speaking,  in  the  submucosa  and  between  the 
villi.     In  the  drawing,  their  bases  do  not  all  appear  in  the  sub- 
mucosa, inasmuch  as  the  nodules  are  cut  in  different  planes.) 

4.  Muscularis  mucosae.     (a)  The  elongate  nuclei  of  the 
involuntary  muscular  element. 

5.  The  submucosa.    (a)   The  blood-vessels,    (b)  Lymph- 
spaces.     (Lymphatic  channels  are  very  irregular  in  form  and  size, 
and  are  often  mistaken,  in  sections,  for  ruptures  in  the  connective 
tissue.     The  stained  nuclei  of  the  endothelial  cells,  with  which  all 
lymph  channels  are  lined,  will  enable  you  to  differentiate.)     (c) 
Glands  of  Brunner.     (There  are  none  shown  in  this  section. 
The  glands  consist  of   convoluted,  branching  tubes  which   pene- 
trate from  the  crypts  to  the  submucosa.     They  are  lined  with 
columnar  epithelium,  and  as  they  are  divided  in  a  section,  they 
resemble  very  nearly  a  crypt  of  Lieberkuhn.     Extensive  groups  are 
found  in  the  duodenum  at  its  pyloric  origin.) 

(H.) 

6.  The  villi.  (a)  The  covering  columnar  cells,  (b)  Beaker 
cells  scattered  between  the  last.     (These  beaker,  goblet,  or  mucous 
cells  are  well  shown  in  the  intestine  of  the  dog  or  rabbit.)     (c) 
The  lacteals.     (These  are  not  plainly  demonstrable,  under  ordi- 
nary circumstances,  in  human  tissue.     Sections  from  the  gut  of  a 
dog  killed  during  the  active  digestion  of  materials  rich  in  hydro- 
carbons, will  show  them  filled  with  minute  fat-globules.)     (d)  The 
basis  tissue,  a  fibrous  reticulum  containing  many  lymphoid  cells. 
(e)  Portions  of  the  capillary  plexuses. 

7.  Blood-vessels  of  the  mucosa  below  the  villi. 

8.  The  adenoid  tissue  of  the  lymph  nodules. 


94 


PRACTICAL    MICROSCOPY. 


THE  LUNG. 
BRONCHIAL  TUBES. 

At  the  root  of  each  lung  the  large  primary  bronchus  enters, 
and  immediately  divides  into  two  equal  branches— dichotomously. 
It  is  evident  that  if  this  mode  of  subdivision  were  continued,  the 


FIG.  69.— DIAGRAM  SHOWING  THE  PLAN  OP  SUBDIVISION  OP  BRONCHI,  IN  THE  HUMAN  LUNG. 
As  the  main  bronchus  enters  the  organ  it  is  seen  to  divide,  dichotomously,  until  the  result- 
ant branches  become  quite  small— say  one-tenth  inch.  These  small  bronchi  now  pursue  a 
straight  course  toward  the  periphery  of  the  lung,  at  the  same  time  giving  off  branches 
spirally.  The  last  divide  dichotomously  and  result  in  the  terminal,  ultimate,  or  capillary 
bronchi. 

periphery  of  the  organ  alone  would  contain  minute  bronchi.  The 
arrangement  is,  however,  such  as  to  give  everywhere  throughout 
the  lung,  bronchial  twigs,  terminal  or  capillary  bronchi,  from  one- 


BRONCHIAL   TUBES.  95 

one-hundredth  to  one-two-hundredth  of  an  inch  in  diameter,  as 
follows : 

The  dic'hotomous  subdivision  is  continued  until  the  resulting 
branches  become  reduced  to  about  one-sixth  of  an  inch  in  diameter, 
when  this  mode  of  division  ceases,  and  the  resulting  tubes  are  pro- 
jected radially  toward  the  periphery  of  the  lung.  As  the  straight 
tubes  pursue  their  course,  side  branches  are  given  off  in  spiral  suc- 
cession. The  side  tubes  themselves  give  off  branches  which  divide 
dichotomously  into  the  terminal  bronchi.  The  straight  tubes  con- 
stantly diminish  in  size,  and  ultimately  divide  and  result  also  in 
terminal  bronchi.  The  diagram  (Fig.  69)  is  intended  to  illustrate 
this  plan  of  subdivision,  but  it  is  purely  schematic. 

A  typical  bronchial  tube  (Fig.  71)  presents  four  coats  as  follows: 

1.  Epithelial. 

2.  Internal  fibrous  or  mucosa. 

3.  Muscular  or  muscularis  mucosw. 

4.  External  fibrous  or  submucosa. 

The  lining  epithelium  is  composed  of  cylindrical  cells,  provided 
on  their  free  extremities  with  delicate  hair-like  appendages — the 
cilia.  Between  the  pointed,  attached  end  of  the  ciliated  cells, 
small  ovoid  cells  are  wedged,  and  the  whole  rests  upon  a  layer  of 
round  cells.  The  epithelium  pursues  a  wavy  course,  so  that  the 
lumen  of  a  tube  appears  stellate  rather  than  circular  in  transverse 
section.  This  greatly  increases  the  extent  of  surface. 

The  internal  fibrous  coat  or  mucosa  is  composed  of  a  small 
amount  of  connective  tissue,  which,  just  beneath  or  outside  the 
epithelium,  sustains  collections  of  adenoid  or  lymphatic  tissue.  In 
the  pig,  a  considerable  quantity  of  yellow  elastic  tissue  is  found  in 
the  mucosa  outside  the  adenoid  tissue,  but  the  amount  is  smaller 
in  man.  The  fibres  are  for  the  most  part  disposed  longitudinally. 
Many  nutrient  vessels  from  the  bronchial  artery,  capillaries,  ve- 
nules,  and  lymph-spaces,  are  also  found  in  this  coat. 

The  muscular  coat — muscularis  mucosae — does  not  differ  from 
the  same  layer  in  other  mucous  membranes.  Its  thickness  varies 
in  proportion  to  the  size  of  the  bronchus,  the  smaller  tube  possess- 
ing relatively  the  thicker  walls.  The  fibres  pass  circularly,  and  are 
of  the  non-striated  or  involuntary  variety. 

The  external  coat  or  submocosa  is  largely  composed  of  loose 
connective  tissue,  the  fibres  being  mostly  arranged  circularly.  A 
few  delicate  elastic  fibres  run  longitudinally.  The  external  fibres, 
like  those  of  all  tubes,  ducts,  and  vessels,  are  for  the  purpose  of 
establishing  connection  with  the  organ  or  part  traversed;  so  that 


96 


PRACTICAL    MICROSCOPY. 


it  is  often  difficult  to  demonstrate  the  exact  external  limit  of  a. 
bronchus.  This  coat  is  liberally  supplied  with  nutrient  branches 
from  the  bronchial  artery. 

The  elasticity  and  strength  of  the  larger  and  medium-sized 
bronchi  are  greatly  increased  by  the  presence  of  cartilage  in  the 
form  of  plates,  which  are  imbedded  in  the  external  coat.  They  are 
not  uniform  in  size,  neither  are  they  placed  regularity.  They  fre- 
quently overlap  one  another,  and  two  or  three  may  be  superposed. 
As  the  tubes  become  reduced  in  size  the  plates  become  diminished 
in  frequency — disappearing  altogether  when  a  diameter  of  about 
one-twentieth  of  an  inch  has  been  reached.  The  cartilage  is  of  the 
hyaline  variety;  and  each  plate  is  covered  with  a  dense  fibrous 
coat,  the  pericliondrium,  which  unites  it  with  contiguous  parts. 


FIG.  70.— TRANSVERSE  SECTION  OF  A  PORTION  OP  HUMAN  LUNG,  SHOWING  A  SMALL  BRONCHUS. 

Stained  with  Hsema. 

A.  Lumen  of  bronchus. 

B.  Ciliated  columnar  epithelium. 

C.  Internal  fibrous  layer — Mucosa. 

D.  Muscular  coat. 

E.  External  fibrous  layer— Submucosa. 

F.  Pulmonary  artery. 

G.  Nerve. 

H,  H,  H.    Pulmonary  alveoli  surrounding  bronchus.    X  60. 

The  principal  bronchi  are  provided  with  a  great  number  of 
mucous  glands,  which  are  located  in  the  external  coat  or  sub- 
mucosa.  They  are  simple,  coiled  tubular  glands;  commencing  on 
the  inner  surface,  penetrating  the  mucosa  and  muscularis  mucosae, 
and  terminating  in  the  submucosa,  generally  within  the  cartilage, 
where  they  are  coiled  in  short,  close  turns  resembling,  in  sections, 
somewhat  the  larger  sweat-glands  of  the  skin.  The  ciliated  epi- 


BRONCHUS    OF   PIG.  97 

thelium  of  the  bronchus  is  continued  down  the  beginning  of  the 
tube  for  a  short  distance,  after  which  the  cells  are  shortened,  and 
lose  their  cilia.  The  coiled,  gland-part  of  the  tube  is  lined  with 
conical  cells,  which  are  so  large  as  to  leave  the  lumen  very  small. 
Sometimes,  and  especially  in  the  aged,  an  ampulliform  dilatation 
of  the  tube  may  be  seen  during  its  passage  through  the  mucosa. 

The  description  just  given  will  apply  to  large  and  medium-sized 
bronchi.  Very  important  changes  take  place  as  we  pass  to  the 
terminal  tubes. 

As  the  tubes  decrease  in  size,  the  first  coat  to  diminish  in  thick- 
ness is  the  outer,  or  submucosa.  We  have  already  alluded  to  the 
disappearance  of  the  cartilage,  and  the  mucous  glands  are  lost  at 
about  the  same  time.  The  outer  coat  becomes,  in  the  small 
bronchi,  so  thin  as  to  be  no  longer  distinctly  demonstrable.  The 
muscular  coat  is  the  last  to  disappear.  It  remains  a  prominent 
feature  of  the  tube  as  long  as  separate  coats  can  be  distinguished. 
The  epithelial  cells  lining  the  tubes  toward  the  termini  become 
shortened,  and,  getting  lower  and  lower,  at  last  result  in  flat,  pave- 
ment epithelium. 

The  walls  of  terminal  bronchi  (diameter  one-one-hundredth  to 
one-two-hundredths  of  an  inch)  are  composed  of  a  slight  amount 
of  connective  tissue  in  which  an  occasional  non-striated  muscle-cell 
and  yellow  elastic  fibre  can  be  distinguished.  They  are  lined  with 
a  single  layer  of  flat  cells.  No  definite  layers  are  distinguishable 
in  these  bronchi.  In  a  transverse  section  the  lumen  would  appear 
circular. 

PRACTICAL   DEMONSTRATION. 

The  histology  of  the  bronchi  can  be  studied  to  best  advantage, 
using  tissue  from  a  freshly-killed  pig  or  sheep.  Short  pieces  of 
tubes,  about  one-quarter  of  an  inch  in  diameter,  from  which  most 
of  the  lung  substance  has  been  cut  away,  should  be  hardened 
quickly  in  strong  alcohol.  Transverse  sections  can  be  made  free- 
handed, or  the  tissue  may  be  infiltrated  with  bayberry  tallow  or 
celloidin,  and  cut  with  the  microtome.  Stain  with  haema.  and 
eosin,  and  mount  in  dammar. 

TRANSVERSE   SECTION   OF    PORTION   OF    BRONCHUS 

OF  PIG.     (Fig.  71.) 
OBSERVE  : 
(L.) 

1.  The  epithelial  lining:  (a)  The  wavy  course,  (b)  Regions- 
occupied  by  bearer  or  goblet  cells.  (The  letter  E  in  the  draw- 


PRACTICAL    MICROSCOPY. 

ing  leads  to  such  a  group.)     (c)  The  number  of  nuclei,  indicating 
the  presence  of  more  than  a  single  layer  of  cells. 

2.  The  mucosa.     (a)  Deeply-stained  blue  nuclei  of  the  ade- 
noid tissue  just  beneath  the  epithelium,     (b)  Pink  portion  of  the 
region  below  the  adenoid  tissue.     (The  longitudinal  elastic  fibres 
cut  transversely.)     (c)  Blood-vessels. 

3.  The  muscular  coat,     (a)  Apparent  solution  of  continuity 
in  places  caused  by  tubes  of  mucous  glands.     (#)  The  absence 
of  large  vessels  in  this  coat. 

4.  The  external  layer,     (a)  Its  extent.     (It  includes  the 


FIG.  71.— TRANSVERSE  SECTION  OF  PART  OF  THE  WALL  OF  A  LARGE  BRONCHUS. 

Lung  of  Pig.    Stained  with  Haema.  and  Eosin.     x  60. 

E.    Epithelial  lining.    The  line  from  the  letter  leads  to  a  part  of  the  lining  containing; 
large  mucous  cells. 
I.     The  internal  fibrous  coat. 
M.    Muscular  coat. 

C.  Cartilage  plates  of  external  fibrous  coat. 

A.    Bronchial  artery.    The  pulmonary  artery  is  not  included. 
V.    Bronchial  vein. 
N.    Nerve  trunk. 
G.    Mucous  glands. 

D.  Obliquely  sectioned  duct. 


THE    PULMONARY    BLOOD-VESSELS.  99 

remainder  of  the  section.)  (b)  Large  cartilage  plates,  C,  stained 
blue,  (c)  Cartilage  cells.  (Note  their  differing  forms  and  dis- 
position in  rows  next  the  surfaces  of  the  plates.)  (d)  Periosteum, 
stained  pink,  (e)  Mucous  gland  coils.  (They  are  usually  be- 
tween the  cartilage  and  the  muscular  coat.)  (/)  Section  of  bron- 
chial arteries  and  veins,  (y)  Collections  of  adipose  tissue  on 
the  outer  surface,  (li)  Portion  or  whole  of  pulmonary  artery 
and  medullated  nerve  trunks  outside  of  and  accompanying  the 
bronchus.  (They  do  not  appear  in  the  illustration.) 

(H.) 

5.  Epithelial  lining,  (a)  Cilia  of  columnar  cells,  (b)  The 
ovoid  cells  between  the  tapering  columnar  cells.  (6-)  The  round 
cells,  "  basement  membrane/'  upon  which  the  columnar  cells  rest. 
(d)  The  goblet  or  beaker  ceils. 

G.  The  mucosa.  («)  The  reticulum  of  the  adenoid  tissue. 
(Will  appear  only  where  the  lymph-corpuscles  have  been  accident- 
ally brushed  out.)  (b)  The  transversely  divided  ends  of  the 
elastic  fibres.  (They  appear  as  a  pink  mosaic.)  (c)  Capillaries. 
(They  may  frequently  be  traced  for  a  considerable  distance  in  their 
tortuous  course.) 

7.  The  cartilage  plates,     (a)    Several  cells  in  a  single 
cavity,     (b)  The  intracellular  network. 

8.  The  mucous  glands,      (a)    That  some  of  the  cells   are 
stained  precisely  like   the  (other)  mucous  cells,  the  beakers. 
(b)  If  possible,  a  gland  tube  leading  up  to  the  lumen  of  the 
"bronchus.     (An  ampulliform  dilatation  is  shown  in  the  upper  part 
of  the  drawing.) 

THE   PULMOffABY   BLOOD-VESSELS. 

The  prominent  accompaniments  of  the  bronchus,  at  the  root  of 
the  lung,  are  the  pulmonary  artery  (carrying  venous  blood)  and 
the  pulmonary  veins. 

The  pulmonary  artery  enters  the  lung  with  the  bronchus,  fol- 
lowing in  its  ramifications,  to  end  in  capillary  plexuses  in  the  wall 
of  the  sac-like  dilatations,  which  are  in  connection  with  the  ulti- 
mate bronchi.  The  blood  is  then  collected  in  venules,  which  unite 
to  form  the  pulmonary  veins.  The  latter  pursue  an  independent 
course  in  their  exit,  not  accompanying  the  bronchi  until  the  root 
of  the  lung  (nearly)  has  been  reached. 

The  bronchial  artery  (nutrient)  enters  with  the  bronchus,  sup- 
plying its  walls  and  the  connective-tissue  framework  of  the  lung. 


100  PRACTICAL    MICROSCOPY. 

A  considerable  amount  of  connective  tissue  accompanies  and 
supports  the  organs  which  enter  the  lung,  and  is  eventually  in 
connection  with  the  fibrous  framework  of  the  organ. 

The  lung  will,  therefore,  be  seen  to  differ  from  organs  generally, 
in  that  it  contains  two  distinct  vascular  .v//y //;//>*,  viz.:  1.  The  pul- 
monary (of  venous  blood),  entering  for  the  purpose  of  its  own  oxy- 
genation;  2.  The  bronchial  (arterial),  which  corresponds  to  the  usual 
nutrient  blood-supply  of  organs. 

THE   PLEUEA. 

The  lung  is  completely  enveloped  with  a  membrane  composed 
externally  of  pavement  epithelium,  while  the  visceral  portion  is 
made  up  of  interlacing  fibrous  and  elastic  tissue.  The  deep  or 
visceral  layer  of  the  pleura  sends  prolongations  in  the  form  of 
septa  into  the  substance  of  the  lung,  dividing  it  into  rounded  poly- 
hedral compartments  or  lobules.  The  interlobular  septa  have 
usually  become  prominent  in  the  human  adult  from  deposits  of 
inhaled  carbon  in  their  lymph-channels. 

THE   PULMONARY   ALVEOLI. 

The  lung  is  constantly  employed  in  maintaining  the  integrity 
of  the  blood.  This  is  accomplished  by  the  exposure  of  the  latter 
to  a  continual  supply  of  atmospheric  air.  The  air  is  introduced 
into  little  sacs  (termed  air-vesicles  or  alveoli),  in  the  walls  of  which 
the  blood  is  distributed  in  a  capillary  plexus.  The  air  does  not 
reach  the  capillaries  themselves,  inasmuch  as  they  are  covered  with 
a  layer  of  flat  cells.  These  cells,  constituting  the  parenchyma  of 
the  lung,  have  the  power,  on  the  one  hand,  of  selecting  such  ma- 
terial from  the  air  as  may  be  required,  passing  it  on  to  the  blood 
in  the  capillaries;  and,  on  the  other,  of  removing  effete  materials 
from  the  blood,  transferring  it  to  the  atmospheric  contents  of  the 
air-sacs  for  exhalation. 

The  air-sacs  or  alveoli  are  not  unlike  minute  bladders.  Their 
diameter  about  equals  that  of  a  terminal  bronchus,  viz.,  from  one- 
one-hundredth  to  one-two-hundredth  of  an  inch.  A  group  of  these 
alveoli  are  associated  in  the  manner  shown  in  Fig.  72,  their  con- 
tiguous walls  fusing  and  all  opening  into  a  common  cavity,  the 
infundibulum.  The  whole  is  in  connection  with  a  terminal 
bronchus  (vide  Fig.  73).  A  primary  lobule  having  been  thus  con- 
structed, several  are  associated  and  united  to  a  slightly  larger 
bronchial  twig,  and  there  results  one  of  the  polyhedral  lobules, 


THE    PULMONARY    ALVEOLI. 


101 


previously  mentioned  as  visible,  especially  on  the  surface  of  the 
lung.     By  a  repetition  of  such  elements  the  lung  is  constructed. 

The  wall  of  a  pulmonary  alveolus  or  air-sac  is  composed  of 
connective  tissue,  supporting  the  capillary  network,  with  a  con- 
siderable amount  of  elastic  tissue  and  an  occasional  muscular  fibre. 
The  whole,  as  we  have  said,  is  lined  with  a  single  layer  of  flat  pave- 
ment epithelium.  The  capillary  plexus,  when  filled  with  blood, 


FIG.  72  -  DIAGRAM  OP  AX  ULTIMATE  PULMONARY  LOBULE. 

A.  A  terminal  bronchus. 

B.  The  air-sacs  or  alveoli. 

affords  the  most  prominent  feature  of  the  wall;  but  when  the  ves- 
sels have  been  emptied  of  their  contents,  they  become  very  insig- 
nificant under  the  microscope,  and  the  fibro-elastic  tissue  becomes 
more  apparent.  You  will  have  observed  that,  aside  from  the  vas- 
cular supply,  the  histology  of  an  alveolar  wall  resembles  very 
closely  that  of  a  terminal  bronchus,  and  when  the  vessels  are  all 
empty  it  is  frequently  difficult  to  differentiate  them  in  the  mounted 
section. 


FIG.  73.— DIAGRAM  SHOWING  AN  ULTIMATE  PULMONARY  LOBULE  |IN  LONGITUDINAL  SECTION, 
SHOWING  THE  MANNER  IN  WHICH  THE  ALVEOLI  ARE  ASSOCIATED  IN  CONNECTION  WITH  A 
TERMINAL  BRONCHUS. 

A.  Terminal  bronchus,  entering 

B.  The  infundibulum. 

C.  C,  C.    Alveoli. 

Fig.  74  shows  a  single  alveolus,  the  vessels  of  which  have  been 
injected  with  a  solution  of  colored  gelatin.  The  alveolus  has  been 
divided  through  the  middle,  and  shows  as  a  cup-shaped  cavity. 


102 


PRACTICAL    MICROSCOPY. 


The  fibrous  marginal  walls  are  indicated  with  their  tortuous  capil- 
laries. The  epithelial  cells  lining  the  bottom  are  obscured  by  the 
opaque  capillaries,  and  shown  only  between  the  loops.  It  is  probable 
that  these  cells  cover  the  plexus  completely  as  they  line  the  alveoli. 
We  now  encounter  an  obstacle  which  will  frequently  be  met  in 
our  study  of  organs.  It  consists  of  the  difficulty  in  recognizing  in 
sections  the  plan  of  structure  which  we  have  learned  is  peculiar  to 
the  organ  under  consideration.  For  example:  A  lung  has  been 
compared  to  a  tree.  The  bronchi  are  the  representatives  of  the 
branches,  and  the  air-sacs  of  the  fruit.  Well,  we  make  a  section 


FIG.  74.— TRANSVERSE  SECTION  OP  A  SINGLE  PULMONARY  ALVEOLUS.    Capillaries  injected. 
Stained  with  Haema.  and  Eosin.     x  400. 

A,  A,  A.    Walls  of  the  alveolus 

B,  B.    Injected  capillaries. 

C,  C.    Pavement  cells  lining  the  alveolus.    These  cells  cover  the  capillaries,  but  do  not  so 
appear  in  the  drawing,  as  the  latter  are  filled  with  an  opaque  injection.    The  observer  is 
supposed  to  be  above  the  sectioned  alveolus,  viewing  the  cup-shaped  cavity. 

from  human  lung — it  matters  little  as  to  the  direction — with  every 
possible  care,  and  the  image  in  the  field  of  the  microscope  resem- 
bles a  fragment  of  ragged  lace  more  nearly  than  anything  else! 
The  arrangement  of  the  tubes  and  alveoli  of  the  lung  has  been  de- 
termined by  filling  the  cavities  with  melted  wax  which,  when  cold> 


LUNG   OF   PIG.  103 

and  the  tissue  destroyed  by  acid,  gives  a  perfect  mould  of  the 
organ.  A  section  gives  us  but  a  single  plane,  and  this  fact  must  be 
always  borne  in  mind. 


PRACTICAL   DEMONSTRATION. 

With  a  very  sharp  razor,  cut  half-inch  cubes  from  pig's  lung. 
Select  portions  free  from  large  bronchi,  with  the  pleura  on  one 
side  at  least,  and  harden  with  strong  alcohol.  Human  lung,  as  fresh 
as  possible,  may  be  treated  in  the  same  manner.  The  epithelium 
of  the  alveoli  shows  best  in  young  lung.  Pieces  of  foetal  lung  are 
easily  hardened,  and  should  be  studied  with  reference  to  medico- 
legal  work.  Lung  must  be  made  very  hard,  or  thin  sections  can- 
not be  cut.  If  the  ordinary  95^  alcohol  does  not  harden  suffi- 
ciently, the  process  may  be  completed  by  transferring  the  tissue 
for  twenty-four  hours  to  absolute  alcohol.  The  celloidin  infiltrat- 
ing process  is  well  adapted  to  this  structure. 

Stain  human  lung  sections  with  borax-carmine,  and  pig's  with 
hsema.  and  eosin.  Mount  in  dammar. 


FIG.  75.— SECTION  OF  LUNG  OP  PIG.    Stained  with  Haema.  and  Eosin.     X  60. 

A,  A.    Infundibula  in  T.  S. 

B,  B,  B.    Alveoli ;  so  sectioned  as  to  show  the  outline  only. 

C,  C,  C.    Alveoli ;  so  sectioned  as  to  present  cup-shaped  cavities. 

D,  ]},  D.    Alveoli ;  sectioned  so  as  to  divide  the  top  (or  bottom). 

E,  E.    Terminal  bronchi  in  T.  S. 


104 


PRACTICAL    MICROSCOPY. 


SECTION   OF   LUNG   OF   PIG.     (Vide  Fig.  75.) 

OBSERVE  : 
(L.) 

1.  The  large  scalloped  openings  A  A,  transversely  divided 
infundibula. 

2.  The  divided  alveoli  B  B,  so  sectioned  as  to  cut  off  both 
bottom  and  top,  and  show  no  epithelial  lining  excepting  at 
inner  edge  of  periphery. 

3.  The  alveoli  C  C,  divided  so  as  to  show  a  cup-shaped  bottom 
or  top.     (The  minute  granules  are  the  nuclei  of  the  lining  cells.) 

4.  The  alveoli  D  D,  so  cut  as  to  leave  most  of  bottom  or  top, 
showing  an  opening  in  the  centre  where  the  sac  has  been  sliced 
off. 


FIG.  76.— TRANSVERSE  SECTION  OF  A  SINGLE  PULMONARY  ALVEOLUS.     Stained  with  Haema. 

X  400. 

A.  A,  A.    Walls  of  alveolus. 

B.  Lumen. 

C.  C,  C.    Capillaries  variously  sectioned  in  their  tortuous  course. 

D.  Pavement  epithelia  intact. 

E.  Detached  pavement  cell. 

F.  Detached  cluster  of  pavement  cells. 
F'.    Granular  lining  cells. 

G.  Pulmonary  artery. 


HUMAN   LUNG.  105 

5.  Openings,  E  E,  which  are  about  the  same  size  and  bear  a 
general  resemblance  to  those  of  Obs.  2.  (Note  that  their  internal 
edges  are  smooth  and  not  ragged.  They  are  terminal  bronchi. 
No  larger  bronchi  have  been  included  in  the  section.) 


HUMAN   LUNG,  SECTION  SHOWING  A  SINGLE 
ALVEOLUS.     (Fig.  76.) 

OBSERVE: 

(L.) 

1.  The  outline  of  alveolus.     (The  alveoli  in  human  lung  will 
show  much  distortion,  as  the  tissue  cannot  be  secured  in  perfect 
condition.) 

(H.) 

2.  The  fibrous  wall  A  A. 

3.  The  lumen   B.     (The  bottom  or  top  has  been  cut  off  in 
making  the  section.) 

4.  The  tortuous  capillaries  0  0,  in  the  fibrous  wall. 

5.  The  lining  epithelial  cells,     (a)   Those  remaining  at- 
tached to  the  edges  of  the  wall  D.     (b)  Detached  cells  E.     (c) 
Groups  partly  detached  F. 

6.  The  divided  pulmonary  artery  G.     (A  medium-sized  bron- 
•chus  existed  in  the  section  immediately  to  the  left  of  the  artery.) 

7.  Portions  of  the  capillary  plexuses  in  other  alveoli  (not 
shown  in  the  figure),  and  especially  demonstrable  when  they  may 
happen  to  contain  blood-corpuscles. 


106  PKACTICAL    MICKOSCOPY. 


THE    LIVER. 

This  great  gland  is  covered  with  a  fibrous  membrane — the  cap- 
sule of  Glisson.  The  capsule  is  covered  with  a  single  layer  of  ir- 
regularly shaped,  flat  epithelial  cells. 

Prolongations  from  the  fibrous,  visceral  portion  of  Glisson's 
capsule  penetrate  the  organ  from  every  side,  and  divide  the  entire 
structure  into  compartments,  the  lobules. 

The  hepatic  lobules  are  irregularly  polygonal  in  transverse  sec- 
'tion,  and  somewhat  ovoid  vertically.  They  are  about  one-twelfth 
inch  in  diameter. 

Let  us  first  examine  the  general  plan  of  the  vascular  arrange- 
ment, and  later,  the  minute  structure  of  the  lobular  parenchyma. 

The  hepatic  blood-supply  comes  from  two  sources:  1st,  The 
venous  drainage  from  the  chylopoietic  viscera  collected  in  the  por- 
tal vein.  2d,  Arterial  supply,  provided  directly  from  the  aorta  by 
the  hepatic  artery.  The  portal  venous  blood  is  filtered  through 
the  liver  instead  of  passing  directly  to  the  ordinary  destination  of 
such  blood  (the  cava),  in  order  to  contribute  certain  factors  to  the 
processes  of  digestion  and  metabolism,  while  the  smaller  arterial 
supply  is  distinctly  nutritive.  The  hepatic  duct  is  the  common 
excretory  conduit  of  the  bile  after  its  formation  by  the  parenchyma 
from,  mainly,  the  portal  blood. 

The  scheme  of  the  organ  will  be  understood  by  reference  to 
Fig.  77,  which  is  purely  diagrammatic. 

The  portal  vein  enters  the  liver  at  the  transverse  fissure.  It 
divides,  subdivides,  and,  reaching  every  part  of  the  various  lobes, 
the  terminal  twigs  are  seen  in  the  connective  tissue  of  the  walls 
of  the  lobules. 

Branches  from  these  portal  termini  or  interlobular  veins  pene- 
trate the  lobular  areas,  and  immediately  break  up  into  capillaries, 
which  form  an  intricate  plexus  throughout  the  lobule.  The  blood 
from  these  capillaries  is  finally  collected  in  a  central  or  intralobular 
vein  by  means  of  which  it  is  immediately  drained  from  the  lobule. 

The  central  veins,  from  a  number  (varying)  of  the  lobules, 
unite  outside  of  the  latter,  forming  the  beginning  of  the  hepatic  or 
so-called  sublobular  veins ;  and,  like  vessels  from  other  lobular 
areas,  unite,  forming  several  (six  or  seven)  large  liepatic  veins  which, 
passing  in  the  connective-tissue  framework,  finally  drain  the  blood 
from  the  organ  and  pour  it  into  the  ascending  cava  as  it  lies  pos- 
teriorly in  its  fissure. 


THE    LIVER. 


107 


The  hepatic  artery  also  penetrates  the  transverse  fissure.  It 
accompanies  the  portal  vein  in  its  ramifications,  giving  off  nutrient 
twigs  to  the  connective-tissue  framework  and  to  the  walls  of  the  ves- 

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The  terminal  branches,  very  minute,  pour  any  remaining 
blood  into  the  venous  plexus  at  the  margin  of  the  lobules,  thus 
providing  arterial  blood  for  the  lobular  parenchyma. 


108  PKACTIC A L    M  1C IIOSCOP Y . 

The  hepatic  duct  is  also  seen  emerging  from  the  transverse  fis- 
sure. (For  sake  of  clearness,  we  will  trace  it  from  without  in- 
ward.) It  follows  the  courses  of  the  portal  vein  with  the  hepatic 
artery.  Wherever  in  a  section  of  the  organ  the  portal  is  divided, 
the  artery  and  duct  will  also  appear.  Bound  together  with  con- 
nective tissue,  the  trio  reach  the  walls  of  the  lobules.  The  ducts 
now  penetrate  the  lobules  and  break  up  into  an  exceedingly  minute 
plexus — the  bile  capillaries.  This  plexus  properly  begins  in  the 
lobules  and  drains  the  bile  as  formed,  passing  it  into  the  ducts  in 
the  opposite  direction  of  the  portal  blood  current. 

THE   PORTAL   CANALS. 

If  it  were  possible  to  grasp  the  vessels  as  they  are  found  emerg- 
ing at  the  transverse  fissure,  the  portal  vein,  hepatic  artery,  and 
hepatic  duct,  and  to  forcibly  tear  them,  with  their  supporting  con- 
nective tissue,  out  of  the  liver,  a  series. of  channels  or  canals  would 
thereby  be  formed.  A  portal  canal,  then,  is  the  space  in  the  liver 
occupied  by  the  portal  vein,  the  liepatic  artery,  the  hepatic  duct,  and 
the  contiguous  connective  tissue.  Frequently  more  than  one  speci- 
men of  each  vessel  is  to  be  seen  in  the  canals.  There  may  be  two 
or  three  veins,  and  as  many  arteries  and  ducts,  associated  in  a  sin- 
gle portal  canal.  Lymphatic  chinks  are  also  abundant  in  this 
connective  tissue. 

From  what  has  been  said,  it  will  be  understood  that  a  vessel 
found  by  itself  in  this  organ  must  be  either  a  central  or  an  liepatic 
vein;  and  these  are  easily  distinguished,  as  the  former  are  within, 
while  the  latter  are  without  the  lobules  and  in  the  connective-tissue 
framework.  On  the  other  hand,  a  group  of  vessels  will  indicate  a 
portal  canal,  with  its  large  and  thin-walled  vein,  the  small  thick- 
walled  artery,  and,  intermediate  in  size,  the  duct. 

THE   LOBULAR  PARENCHYMA. 

The  lobules  consist  of  two  capillary  plexuses,  one  containing 
blood  and  the  other  bile.  In  the  meshes  of  this  network,  the 
hepatic  cells  are  located. 

The  blood  capillaries,  although  extremely  tortuous,  have  a  gen- 
eral direction  of  convergence  toward  the  central  veins.  This  is 
best  seen  when  the  lobules  have  been  divided  in  a  vertical  direction. 

The  bile  capillaries  are  among  the  smallest  canals  found  in  vas- 
cular tissues,  having  a  diameter  of  one-twelve-thousandth  of  an 
inch.  They  pursue  a  direction  in  the  human  liver,  as  a  rule,  at 
right  angles  to  the  course  of  the  blood  capillaries,  and  are  not  de- 


THE   LOBULAR   PARENCHYMA. 

monstrable,  except  with  considerable  amplification,  say  X  400,  and 
then  only  in  the  thinnest  portion  of  the  sections.  They  are,  prop- 
erly speaking,  merely  minute  channels  in  the  parenchyma,  and 
have,  it  is  believed,  no  wall. 

The  hepatic  cells  are  polyhedral,  about  twice  the  size  of  a  white 
blood-corpuscle,  say  one-one-thousandth  of  an  inch,  usually  with  a 
single  nucleus  and  with  granular  protoplasm,  frequently  contain- 
ing minute  fat  droplets  and  granules  of  yellow  pigment.  The  ex- 
istence of  a  definite  limiting  membrane  has  been  questioned,  as  far 
as  the  cell  of  human  liver  is  concerned,  although  such  structure 
can  be  shown  in  many  of  the  lower  animals. 

The  physiological  plan  of  the  intralobular  structure  is  expressed 
in  the  diagram,  Fig.  78.  The  blood  is  brought  into  relation  with 


FIG.  78.— DIAGRAM  ILLUSTRATING  THE  INTRA-LOBULAR  HISTOLOGY  OF  THE  LIVER. 
The  hepatic  cells  are  connected  in  columns  between  the  blood-capillaries.  The  cells  are 
endowed  with  the  power  of  selecting,  especially,  such  materials  from  the  blood  as  are  neces- 
sary for  the  manufacture  of  bile.  Having  accomplished  this,  the  secreted  fluid  is  given  up 
to  the  bile-capillaries,  and  by  them  poured  into  the  ducts,  and  led  out  of  the  liver  for 
subsequent  use.  The  direction  of  the  pressure  is  indicated  by  the  arrows.  This  is  the  his- 
tology of  gland  structures  generally. 

the  lobular  parenchyma — the  hepatic  cells — by  the  capillary  plexus, 
and  the  elements  necessary  to  constitute  the  bile  are  selected  and 
carried  on,  to  be  drained  away  by  the  bile  capillaries  and  ducts. 

PRACTICAL   DEMONSTRATION. 

It  is  best  to  begin  with  the  liver  from  a  pig.  The  amount  of 
connective  tissue  in  the  normal  human  liver  is  very  small,  and  is 
mainly  confined  to  the  support  of  the  interlobular  vessels;  the 
boundaries  of  the  lobules  are,  therefore,  poorly  defined,  and  with- 
out the  previous  observation  of  some  well -outlined  specimen,  I  find 


110  PRACTICAL    MICROSCOPY. 

the  student  frequently  gets  but  an  imperfect  notion  of  the  plan  of 
the  human  organ. 

Pieces  of  liver,  say  one-half  inch  square  by  a  quarter  of  an  inch 
thick,  are  hardened  by  twenty-four  hours'  immersion  in  strong 
alcohol.  Larger  pieces  may  be  prepared  with  Miiller's  fluid.  Sec- 
tions should  be  cut  with  a  microtome,  care  being  taken  to  include 
the  transverse  division  of  some  of  the  medium-sized  portal  canals. 
The  portal  vein,  with  its  accompanying  vessels,  may  be  easily  dis- 
tinguished from  the  solitary  and  less  frequent  branches  of  the 
hepatic  veins.  The  elements  of  these  canals,  and  especially  the 
larger  ones,  are  best  kept  intact  by  infiltration  of  the  tissue  with 
celloidin;  but  very  fine  sections  may,  with  care,  be  made  from  the 
alcohol-hardened  tissue.  Even  free-hand  cuts,  after  some  degree 
of  skill  has  been  obtained  by  practice,  will  answer  very  satisfacto- 
rily. Stain  with  hsema.  and  eosin. 


SECTION   OF    LIVER   OF    PIG.     CUT  VERTICALLY   TO 
AND   INCLUDING   THE   CAPSULE   OF   GLISSON. 

(Fig.  79.) 
OBSERVE : 

(L.) 

1.  The  capsule  of  Glisson  C.  (Note  the  prolongations  sent 
into  the  organ,  which  divide  the  entire  structure  into  irregularly 
polygonal,  if  divided  transversely;   and  elongated,  vertically  sec- 
tioned areas — the  hepatic  lobules.) 

2.  The   central   (intra)  veins  C  V.      (Note  that  the   figure 
formed  by  the  division  of  the  vein  varies  according  to  the  direc- 
tion of  the  cut,  a  circle,  oval,  or  elongated  slit,  as  the  lobules  have 
been  sectioned  transversely,  obliquely,  or  vertically.) 

3.  The  hepatic  veins  H  V.     (Those  shown  in  the  section  are 
undoubtedly  sublobular.     It  must  be  remembered  that  sub  applied 
to  these  vessels  is  misleading,  as  the  lobules  are  situated  on  every 
side,  as  well  as  above  the  sublobular  veins.) 

4.  The  portal  canals  P  C.     (Even  the  smaller  ones,  I,  are  read- 
ily differentiated  from  areas  containing  hepatic  veins,  inasmuch  as 
a  group  of  vessels  can  be  distinguished — the  hepatic  veins  running 
solus.) 

5.  The  portal  veins  V.     (Observe  that  they  usually  present 
as  the  largest  element  of  the  canals.     Note  their  thin  walls,  the 
same  fusing  insensibly  with  the  surrounding   connective   tissue. 
They  not  infrequently  contain   blood-clots,  with  deeply   stained 
scattering  white  corpuscles,  appearing  with  this  amplification  as 
dots  or  granules. 

6.  Hepatic  arteries  A.     (The  larger  examples  may  be  deter- 


LIVER   OF   PIG. 


Ill 


mined  by  their  thick  muscular  media  and  the  wavy  pink  line — the 
fenestrated  membrane.     Several  may  be  seen  in  a  single  canal.) 

7.  Hepatic  ducts  D.     (These  are  lined  with  cylindrical  cells, 
hexagonal  in  transverse  section,  and  the  bold  deeply-stained  nu- 
clei give  the  ducts  marked  prominence  even  with  the  low  power. 
Indeed,  the  smaller  portal  canals  are  frequently  differentiated  by 
this  element  alone — this  being  especially  true  when  the  structures 
have  been  disturbed,  and  perhaps  torn,  in  the  process  of  mounting.) 

8.  The  lobular  parenchyma.     (The  arrangement  of  the  he- 
patic cells,  forming  branching  columns,  is  merely  indicated— with 


ITiG.  79.— LIVER  OF  THE  PIG  SECTIONED  AT  RIGHT  ANGLES  TO  GLISSON'S  CAPSULE.    Stained 

with  Haeina.  and  Eosin.     x  60. 
C.    Capsule  of  Glisson. 

C.  V.    Central  veins. 

0.  C.    Oblique  section  of  central  veins. 

1,  I,  I.    Inter-lobular  veins.     (In  small  portal  canals.) 
P.  C.    A  large  portal  canal. 

A.  A.    Hepatic  arteries. 

D.  Hepatic  duct. 
V.    A  portal  vein. 

C.    Connective  tissue  from  Glisson's  capsule. 
H.  V.    Hepatic  veins— probably  sub-lobular. 

the  low  power — by  their  deeply-stained  nuclei  presenting  granular 
-areas  within  the  lobular  boundaries.     Still,  by  careful  attention, 


PKACTICAL    MICROSCOPY. 

the  elements  will  be  seen  to  radiate  more  or  less  distinctly  from. 

focal  points — the  central  or  intra-lobular  veins.) 

(H.) 

9.  The  portal  veins.     (Note  the  fusing  of  the  wall  with  the 
surrounding  tissue — it  being  extremely  difficult  to  find  the  line  of 
demarcation.) 

10.  The  lymph  spaces  in  the  connective  tissue  of  the  portal 
canals.     (Note,  in  those  which  are  better  defined,  the  nuclei  of  the 
endothelium.     Do  not  confound  these  lymphatics  with  small  veins 
as  the  latter  present  a  tolerably  defined  wall,  while  the  lymphatic 
chinks  appear  like  rifts  in  the  connective  tissue;   it  would  be  diffi- 
cult to  make  this  distinction  without  the  endothelial  cells.) 

11.  Hepatic  arteries.  (On  account  of  its  solidity,  the  liver 
will  enable  the  student  to  secure  sections  of  blood-vessels  present- 
ing the  typical  structure  more  nearly  than  the  specimens  obtained 
from  the  organs  heretofore  examined.)  Note  (a)  the  elongate 
nuclei  of  the  sarcous  elements  of  the  media;  (b)  the  fusing  of 
the  adventitia  with  the  connective  tissue  surrounding  the  artery; 
(c)  the  sharply  defined  outer  boundary  of  the  intima — the  fen- 
estrated  membrane,  which,  from  the  action  of  the  hardening 
agent,  has  contracted  the  elastic  fibres  and  detached  (d)  the  endo- 
thelial cells.  (Inasmuch  as  the  lining  cells  of  small  arteries  are 
very  frequently  partly  detached  in  alcohol-hardened  tissue,  they 
may  simulate  columnar  cells.  A  like  appearance  is  often  pre- 
sented when  an  artery  has  been  sectioned  obliquely,  by  the  project- 
ing muscle-cells  of  the  media.) 

12.  Hepatic  ducts.  Note:  (a)  The  lining  cylindrical  cells. 
(b)  The  nuclei  of  these  cells  (as  a  rule,  perfectly  spherical;  and, 
in  transections  arranged  in  a  circle,  affording  an  appearance  per- 
fectly characteristic),  (c)  Mucous  glands  in  the  wall  of  the 
larger  ducts,  lined  with  large  nucleated  columnar  cells,  precisely 
like  those  lining  the  duct-lumen;  and,  hence,  liable  to  be  mistaken 
for  small  ducts.  (The  tube  carrying  the  mucus  secreted  in  these 
pocket-like  glands  does  not  pass  directly  into  the  lumen  of  the 
duct,  but  runs  along  obliquely,  much  like  glands  in  the  bronchi. 
Not  infrequently  the  glands  possess  no  proper  efferent  tube,  but 
are  mere  depressions  or  diverticula  in  the  thick  wall  of  the  bile 
duct.) 

13.  The  lobular  parenchyma.  (Single  cells,  partly  detached, 
may  be  found  about  the  edges  of  the  section.)  Note:  (a)  The 
somewhat  polygonal  figure;  (b)  the  nucleus;  (c)  nucleoli;  (d) 
fibrillated,  mesh-like  cell  body ;  and  (e)  an  apparent  cell  wall. 


SECTION    OF   HUMAN   LIVER.  113 

(The  arrangement  of  the  lobular  parenchyma  will  be  noted  in  con- 
nection with  the  human  liver.) 

HUMAN   LIVER.  j 

PRACTICAL  DEMONSTRATION. 

The  sections  from  which  the  illustrations  have  been  drawn 
were  made  from  material  hardened  in  Milller's  fluid.  The  tissue 
vas  then  cut,  the  sections  washed  by  six  hours'  maceration  in 
water,  after  which  they  were  treated  successively  with  alcohol  Nos. 
3,  2,  and  1,  stained  with  haema.  and  eosin,  and  mounted  in  dam- 
mar. This  treatment  aids  greatly  in  the  demonstration  of  the  blood 
capillaries,  as  the  contained  blood- corpuscles,  in  consequence  of 
some  change  effected  by  the  chromium  salt,  take  the  eosin  deeply. 
The  nucleoli  of  cells  are  also  rendered  markedly  prominent. 

Pieces  of  tissue,  a  quarter  of  an  inch  square  by  half  an  inch 
thick,  may  be  hardened  in  alcohol.  This  method  will  give  very 
excellent  results,  providing  the  sections  be  cut  as  soon  as  the  hard- 
ening process  has  become  complete.  Stain  as  above. 

For  the  demonstration  of  the  isolated  hepatic  cells,  scrape  the> 
cut  surface  of  a  piece  of  hardened  liver  with  a  scalpel,  and  throw 
the  scrapings  into  a  watch-glass  of  haema.  After  a  few  moments, 
drain  off  the  stain,  and  brush  the  stained  tissue  elements  into  a 
test-tube  nearly  filled  with  water.  Change  the  water  two  or  three 
times;  and  when  clear,  add  a  few  drops  of  eosin  solution.  Allow 
the  eosin  to  stain  for  a  moment  only;  decant,  drain,  and  fill  the 
tube  with  alcohol.  After  ten  minutes  the  spirit  may  be  drained 
off,  and  the  tube  partly  filled  with  oil  of  cloves.  A  drop  of  the 
sediment  may  then  be  placed  upon  the  slide,  the  bulk  of  the  oil 
removed  with  paper,  and  the  mounting  completed  by  adding  a 
drop  of  dammar  and  the  cover  glass.  I  am  in  the  habit  of  keeping 
this  tissue  in  the  oil,  from  year  to  year,  for  use  in  my  classes.  If 
the  oil  be  pure,  and  the  washing  thorough,  the  staining  will  re- 
main unaffected  for  certainly  two  or  three  years. 

SECTION   OF  HUMAN  LIVER. 

Cut  at  right  angles  to  the  surface,  and  stained  with  haema.  and  eosin. 

(Fig.  80.) 
OBSERVE : 
(L.) 

1.  The  imperfectly  outlined  lobules  (in  consequence  of  the 
absence  of  interlobular  connective  tissue). 

2.  The  fusing  of  the  lobules.     (At  points  like  B  B,  it  is  im- 
possible to  say  just  where  one  lobule  ceases  and  the  contiguous  one 
begins.) 

3.  The  central  (or  intralobular)  veins  A  A — (frequently  ap- 
pearing as  mere  slits  on  account  of  the  direction  of  the  cut). 


]14  PEACTICAL    MICROSCOPY. 

4.  The  portal  canals  G  G.     (These  are  readily  detected  on 
account  of  the  deeply-stained  nuclei  of  the  cells  lining  the  hepatic 
ducts.) 

(H.) 

5.  Portal  canals  (too  small  for  demonstration  of  the  several 
elements,  but  always  distinguishable  by  the  bile-duct  cells). 

6.  The  larger  portal  canals  0.     Note:  (a)  The  large  thin- 
walled  vein  D;  (b)  The  duct  E;  (c)  The  artery  F. 


FIG.  80. — SECTION  OF  HUMAN  LIVER. 
Stained  with  Heema.  and  Eosin.     x  60. 

A.  A,  A.    Central  veins  sectioned  generally  at  right  angles  to  the  lobule. 

B.  B.    Points  where  adjoining  lobules  coalesce.    Illustrating  the  difficulty  of  outlining  the 
lobules  in  normal  human  liver. 

C.  Connective  tissue  of  a  portal  canal. 

D.  Large  interlobular  vein. 

E.  Hepatic  duct  belonging  to  C. 

F.  Hepatic  artery  of  C. 

G.  G.    Smaller  portal  canals. 

H.    Small  hepatic  ducts— always  recognizable  by  the  deeply  haema.-stained  nuclei  of  their 
lining  cells. 
I,  I.    Hepatic — sublobular — veins. 

7.  The  tortuous  course  of  the  hepatic  cell-columns  as  com- 
pared with  the  same  in  the  section  previously  studied. 

8.  The  hepatic  veins.     (Observe  their  infrequency  compared 


ELEMENTS    OF  A   PORTAL   CANAL. 


115 


with  the  sections  of  the  portal  veins.  Note  the  small  amount  of 
connective  tissue  around  them — greater,  however,  than  that  about 
the  central  veins.) 


ELEMENTS  OF  A  PORTAL  CANAL.    From  previous  Section. 

(Fig.  81.) 
OBSERVE  : 
(H.) 

1.  The  portal  vein  V.     (Note  the  nuclei  of  the  few  endo- 
thelia  remaining,  and  the  corpuscular  elements  of  the  blood 


FIG.  81.— SECTION  OF  HUMAN  LIVER  SHOWING  THE  ELEMENTS  OP  A  PORTAL  CANAL. 

Stained  with  Hsema.  and  Eosin.    X  400. 
A.    Hepatic  artery. 
V     Portal  vein— interlobular. 
D.    Hepatic  duct  in  T.  S. 
D.  L.    Hepatic  duct  in  L.  S. 
L.    Lymph  space. 
The  lobular  parenchyma  of  contiguous  lobules  will  be  seen  on  the  right,  and  above  the  canal. 

in  the  lumen  of  the  vein.  Observe  that  the  white  corpuscles  are 
scanty,  and  deeply  stained,  and  that  many  of  the  colored  corpuscles 
are  granular,  and  show  loss  of  pigment  from  action  of  the  alcohol.) 


116  PRACTICAL    MICROSCOPY. 

2.  The  hepatic  artery  A.     (In  the  human  liver,  the  portal 
canals  frequently  carry  a  number  of  arteries  and  ducts,  instead  of 
one  of  each,  as  shown  in  the  one  selected  for  the  illustration.     The 
arteries  can  nearly  always  be  differentiated  by  the  clear  wavy  line 
of  the  fenestrated  membrane.     Should  the  section  have  been  in  a 
longitudinal  direction  with  reference  to  the  vessel,  look  for  the 
elongate  nuclei  of  the  smooth  muscle- cells  of  the  media,  some  run- 
ning with  the  artery — the  longitudinal — and  others  at  right  angles 
to  its  course — the.  circular  fibres.) 

3.  The  hepatic  duct  D.     (Observe  the  thickness  of  the  wall, 
depending,  of  course,  upon  the  diameter  of  the  duct  itself — and  the 
presence  of  connective  tissue  supporting  scattering  non-striped 
muscle-cells.     Note  the  beautiful,  clear,  columnar  cell-lining. 
That  these  cells  are  polygonal  in  transverse  section  is  demon- 
strable at  D  L,  where  the  duct  has  been  cut  in  a  longitudinal  way,, 
and  the  cells  are  seen  from  above. 

4.  The  connective-tissue  element  of  the  canal,  reaching  out 
in  various  directions  between  the  adjacent  lobules. 

5.  Lymph  spaces  or  chinks  L.     (Note  the  stained  nuclei  of 
the  endothelia.) 

6.  Nerve  trunks.     (In  the  larger  canals  bundles  of  medullated 
nerves  may  be  frequently  seen.     They  are  not  shown  in  the  ac- 
companying illustration.) 


THE   LOBULAR   PARENCHYMA.     (Fig.  82.)     STAINED 
CELLS   FROM   HUMAN  AND   PIG'S   LIVER. 

OBSERVE : 

(H.) 

1.  Isolated  hepatic  cells  A,  A.    Note  the  large,  variably- 
sized  nuclei,  their  nucleoli,  and  the  granular  protoplasm  of 
the  cell-body. 

2.  Groups  of  cells  forming  portions  of  the  hepatic  cell-columns 
as  at  C. 

3.  Cells  containing  fat  globules  D.     (This  is  not  necessarily 
a  pathological  process,  although  exactly  resembling  one,  but  the 
physiological  storing  of  hydrocarbons.) 

4.  Doubly  nucleated  cells  B. 


THE    LOBULAK    PARENCHYMA    CONTINUED.  117 


FIG.  82.— ISOLATED  HEPATIC  CELLS.    Stained  with  Haema.  and  Eosin.     x  400. 

A.  A.    Cells  from  human  liver. 

B.  Cells  from  same,  showing  below  a  blood  capillary  in  T.  S. 

C.  A  blood  capillary  with  part  of  a  column  of  cells. 

D.  Human  liver  cells  in  a  condition  of  fatty  infiltration. 

E.  Isolated  cells  from  liver  of  pig,  showing  intracellular  network. 


THE  LOBULAR  PARENCHYMA  CONTINUED.     SECTION 
OF   HUMAN   LIVER. 

Fig.  83.     (Having  found  with  (L.)  a  typical  lobule  in  transverse 
section,) 
OBSERVE  : 
(H.) 

1.  The   central  vein  C.  V.      (Note   the  exceedingly  delicate 
"wall  and  search  for  a  trunk  of  the  intralobular  plexus  in  its  con- 
nection with  this  vein.) 

2.  The  blood  capillaries  in  longitudinal  section,   B,   C. 
(Observe  their  exaggerated  tortuosity,  bifurcation,  and  anas- 
tomoses.) 

3.  Blood  capillaries  in  transection,  T.  S.     (Should  the  capil- 
laries be  filled  with  blood,  this  demonstration  will  be  greatly  aided.) 

4.  Hepatic  cell  columns,  H.  C.     (Note  the  difficulty  with 
which  these  can  be  traced  for  any  great  distance,  on  account  of 
their  irregular  and  twisted  course  throughout  the  lobule.     Ob- 
serve that  the  lobules  are  composed  largely  of  tortuous  blood  capil- 
laries, between  which  the  hepatic  cell-columns  are  placed.     Note 
the  manner  in  which  the  cells  are  disposed  around  the  blood 
capillaries,  as  at  T.  S.) 


118  PRACTICAL    MICROSCOPY. 

5.  Bile  capillaries,  D.  (These  are  rather  difficult  of  demon- 
stration in  the  human  liver.  The  section  should  be  extremely  thin, 
and  a  higher  power  than  we  ordinarily  use  will  be  required.  They 


FIG.  83. — A  SINGLE  LOBULE  FROM  HUMAN  LIVER. 
Transverse  section.    Stained  with  Hsema.  and  Eosin.    x  400. 

C.  V.    Central  vein  of  the  lobule. 
B.  C.    Blood  capillaries  in  L.  S. 

T.  S.    The  same  in  transverse  section. 
H.  C.    Columns  of  hepatic  cells. 

D.  Bile  capillaries. 

are  best  made  out  at  the  junction  of  three  or  four  cells,  where  the 
bile  capillary  has  been  divided  transversely. 


THE   LOBULAR  PARENCHYMA,  CONCLUDED.     ORIGIN 
OF  THE  BILE  DUCTS.     SAME  SECTION  AS  BEFORE. 

(Fig.  84.) 
OBSERVE: 

(H.) 

1.  The  connection  between  the  intralobular  bile  capil- 
laries and  the  marginal  or  intralobular  bile  ducts.  (The  man- 
ner of  connection  between  the  above  is  as  follows :  The  bile  capil- 
laries are  merely  channels  between  the  hepatic  cells,  and  run,  as  a- 
rule,  at  right  angles  to  the  blood  capillaries.  They  are,  I  believe^ 


THE   LOBULAK  PARENCHYMA   CONTINUED. 

in  the  human  liver,  destitute  of  a  wall.  As  these  channels  ap- 
proach the  marginal  part  of  the  lobule,  the  hepatic  cells  surround- 
ing the  capillary  are  seen  to  change  their  form.  They  elongate, 
getting  thinner,  gradually  losing  their  form  as  hepatic  cells,  and 
assume  a  columnar  type.  At  the  same  time,  a  few  fibres  of  con- 
nective tissue  are  thrown  outside  the  modified  hepatic  cells,  and  a  bile 
duct  results.  The  hepatic  cells  become,  insensibly,  the  columnar 


FIG.  84.— PORTION  OF  THE  PERIPHERY  OF  AN  HEPATIC  LOBULE  SHOWING  THE  ORIGIN  OF  A 

BILE  DUCT. 
Stained  with  Hsema.  and  Eosin.     x  400. 

A.  Bile  capillaries  in  longitudinal  section. 

B.  Bile  duct.    The  bile  capillaries  are  simply  chinks  between  the  hepatic  cells.    In  order 
to  the  formation  of  a  duct,  the  hepatic  cells  are  altered  in  shape,  elongated,  and  eventually 
become  the  lining  cells  of  the  duct.    A  little  connective  tissue,  thrown  around  the  outside, 
completes  the  structure  as  seen  at  B. 

C.  Bile  capillary  in  transverse  section.    The  larger  clear  spaces  are  blood  capillaries. 

cells  lining  the  duct.  This  is  shown  in  the  illustration  rather 
diagrammatically.  Its  demonstration  requires  much  patient  study 
and  search.  The  duct  is  best  traced  backward,  as  these  are  readily 
found.) 


120  PRACTICAL    MICROSCOPY. 


THE    KIDNEY. 

The  kidney  is  as  singular  in  structure  as  in  function.  Although 
developed  in  lobular  form,  little  trace  of  this  remains  in  the  adult 
organ. 

The  kidney  consists,  essentially,  of  an  intricate  system  of  blood- 
vessel plexuses,  in  intimate  relation  with  a  system  of  urine  tubes 
— the  whole  supported  by  a  small  amount  of  connective  tissue. 

The  accompanying  drawing  (Fig.  85)  will  serve  to  give  an  idea 
of  the  gross  plan  or  scheme  of  the  structure — remembering  that 
the  illustration  is  only  a  diagram. 

On  making  a  vertico-lateral  section,  on  the  median  line,  the 
following  appears : 

The  kidney  is  invested  with  a  fibrous  capsule,  which  is  con- 
nected with  the  parenchyma  by  very  delicate  prolongations  of  its 
connective-tissue  fibrillae.  This  capsular  investment  is  in  connec- 
tion, above,  with  the  supra-renal  bodies;  and,  on  the  inner  border, 
with  the  vessels,  etc.,  which  enter  and  leave  the  organ  at  its  hilum. 
The  ureter,  penetrating  the  areolar  tissue  which  (containing  much 
fat)  presents  at  the  hilum,  may,  for  clearness  of  description,  be 
traced  backward  into  the  kidney.  This  tube  expands  into  the 
pelvis,  and  reduplications  of  its  wall  imperfectly  divide  the  pelvic 
area  into  three  compartments,  or  infundibula. 

Each  infundibulum  is  subdivided  again,  imperfectly,  into  sev- 
eral pockets  or  calyces  ;  and  into  each  calyx  may  be  seen,  peeping 
from  the  kidney  substance,  a  papillary  eminence  or  apex  of  a  cone 
— the  pyramids  of  Malpighii.  The  pelvis  is  lined  with  a  variety  of 
transitional  or  imperfectly  stratified  epithelium,  which  will  be  de- 
scribed hereafter. 

The  blood-vessels,  lymphatics,  etc.,  pass  in  at  the  hilum,  out- 
side the  ureter,  pelvis,  and  infundibula.  The  artery  divides  into 
numerous  branches  which  are  seen  in  the  diagram  passing  out- 
ward, between  the  Malpighian  pyramids.  The  renal  vein  pursues 
much  the  same  course,  the  main  trunks  lying  side  by  side. 

On  examining  a  section  of  the  kidney,  made  in  the  direction 
indicated  in  Fig.  85,  a  division  will  be  manifest  of  an  outer  por- 
tion, bounded  by  the  capsule  externally,  of  granular  texture,  con- 
taining the  blood-vessels,  etc.  This  is  called  the  cortex.  Within 
the  cortical  portion  there  appear  a  number  of  pyramidal  masses — 
whose  apices  we  have  previously  seen — of  finely  striated  texture — 
the  medullary  or  Malpighian  pyramids.  The  cortical  substance 


THE   KIDNEY.  121 

projects  itself  between  the  pyramids,  completely  isolating  them, 
forming  the  cortical  columns. 

Again  observing  the  outer  cortex,  it  will  present  narrow,  light- 
•colored  lines,  which  converge  toward  the  pelvis;  and,  eventually, 
pass  into,  and  become  a  part  of  the  Malpighian  pyramids.  These 


FIG.  85.—  DIAGRAM  SHOWING  THE  PLAN  OF  STRUCTURE  OF  THE  HUMAN  KIDNEY. 

light  areas,  made  up  of  urine  tubules,  are  •  the  pyramids  of  Ferrein, 
or,  as  sometimes  called,  the  medullary  radii. 

The  darker  spaces  between  the  pyramids  of  Ferrein  are  called 
labyrinths. 

The  gross  elements,  to  be  understood  before  we  proceed,  then, 
are: 

1.  The  capsule  of  the  kidney. 

2.  The  ureter. 

3.  The  pelvis  with  its  three  infundibula.     The  subdivision  of 


122  PEACTICAL    MICROSCOPY. 

each  infundibulum  into  several  calyces.     Each  calyx  the  site  of 
the  apex  of  a  Malpighian  pyramid. 

4.  The  blood-vessels  entering  and  leaving  the  hilum.      Their 
subdivision  outside  the  pelvic  lining,  and  final  passage  into  the. 
kidney  substance  in  the  cortical  columns. 

5.  Division  of  kidney  substance  into  cortex  and  medullary  or 
Malpighian  pyramids. 

6.  Penetration  of  cortical  tissue  inward  between  pyramids  of 
Malpighii — constituting  the  cortical  columns. 

5.  The  pyramids  of  Per  rein. 

6.  The  labyrinths. 

In  the  domestic  animals  there  are  no  cortical  pyramids — the 
pyramids  of  Malpighii  coalescing,  as  it  were — thus  presenting  a 
true  medulla. 

I  have  remarked  that  the  kidney  is  made  up  largely  of  urine- 
carrying  vessels  (the  tubuli  uriniferi)  and  blood-vessels.  We  will 
first  study  the  tubular  system,  reserving  for  the  present  the  consid- 
eration of  the  blood-vessel  arrangement. 

THE    TUBULI    URIKIFERI. 

The  urine-carrying  tubules  commence  in  the  cortex,  and,  after 
taking  a  very  circuitous  route  with  frequently  varying  diameter, 
the  tubes  end  at  the  apex  of  the  pyramids  of  Malpighii,  where- 
they  pour  their  contained  urine  into  the  calyces.  The  urine  then 
overflows  into  the  infundibula,  and  is  finally  drained  from  the 
pelvis  by  the  ureter. 

We  shall  begin  with  a  single  typical  tube;  and,  understanding 
its  histology,  we  can  build  up  the  organ,  by  simply  multiplying 
this  element. 

A  uriniferous  tube,  or  tubule,  commences  in  the  cortex  in  a 
labyrinth  (between  the  pyramids  of  Ferrein),  as  a  thin-walled 
(STMMF")  sac  (rlV)-  This  vesicle,  with  contents,  is  a  Malpighian 
body;  and  its  wall  is  called  the  capsule  of  the  same,  or  the  cap- 
sule of  Bowman.  It  is  made  up  of  connective  tissue  and  is  the 
thickest  part  of  the  uriniferous  tube  wall  or  membrana  propria, 
the  remaining  portion  being  thin  and  homogeneous. 

From  one  side  of  this,  the  expanded  beginning  of  the  tube,  a 
narrow  neck  (ToVo")  is  projected,  which  immediately  widens  (J^Q") 
into  a  tube — the  proximal  convoluted.  This  tube  (or  this  portion 
of  the  tube)  pursues  a  very  tortuous  course,  always  keeping  be- 
tween Ferrein's  pyramids,  and  finally  approaches  the  base  of  a 
Malpighian  pyramid.  Here  it  assumes  an  irregular  spiral  form — 
the  spiral  tube  (^o")- 


THE   KIDNEY. 


The  tube  suddenly  narrows  (-g-gVir")*  becomes  straight,  and 
passes  into  a  pyramid  of  Malpighii.  It  reaches  sometimes  just  into- 
the  pjo-amid,  more  frequently,  however,,  passing  deeper  than  this. 
— often  descending  two-thirds  of  the  distance  to  the  apex;  and  is 
called  the  descending  limb  of  Henle.  Henle's  descending  limb  sud- 


FIG.  86.— DIAGRAM  SHOWING  THE  DIVISIONS  OF  A  KIDNEY  TUBULE. 

denly  turns  upon  itself,  forming  a  loop;  and,  widening  (TOO"O")>  re" 
turns  upon  its  course  as  the  ascending  limb  of  Henle.  It  again 
enters  the  cortex,  keeping  in  a  pyramid  of  Ferrein,  and  passes  out- 
ward until  it  approaches  the  outer  limit  of  the  cortex,  near  the 
capsule  of  the  kidney.  Here  the  ascending  limb  of  Henle  widens 
,  forming  the  distal  convoluted,  which  pursues  a  tortuous 


124  PRACTICAL    MICROSCOPY. 

course  in  the  outer  cortex.  The  distal  convoluted  then  re-enters  a 
pyramid  of  Ferrein,  narrows  (^j"),  and  passes  a  second  time  into 
a  Malpighian  pyramid,  under  the  title  of  straight  or  collecting 
tube,  or  tube  of  Bellini.  The  last,  after  reaching  very  nearly  to 
the  apex  of  the  pyramid,  unites  with  others  of  a  like  character, 
and  forms  principal  tubes  (yj-o-")-  Several  principal  tubes  unite 
to  form  a  papillary  duct  (JOT")-  From  100  to  200  of  the  last  open 
upon  the  surface  of  the  apical  portion  of  a  Malpighian  pyramid. 

It  must  be  borne  in  mind  that,  in  describing  the  tubular  sys- 
tem, although  such  terms  as  "  convoluted  tube/'  "  looped  tube," 
etc.,  are  employed,  these  are  not  separate  tubes,  but  only  names 
applied  to  different  portions  of  one  long  tube.  A  single  tubule,  then, 
commences  at  Bowman's  capsule,  becomes  narrowed  like  the  neck 
of  a  flask;  courses  as  the  proximal  convoluted  and  spiral;  descends 
into,  turns,  and  emerges  from  a  Malpighian  pyramid,  as  Henle's 
looped  portion;  reaches  the  extreme  cortex,  and  swells  as  the  distal 
convoluted;  and  here  ends  as  a  single  or  isolated  tubule  and  enters 
a  straight  tube.  The  straight  tubes  receive  several  distal  convo- 
luted termini,  at  the  cortical  periphery,  and  pass  in  small  bundles 
(forming  the  pyramids  of  Ferrein)  directly  onward  toward  the  apex 
of  a  Malpighian  pyramid;  uniting  with  one  another  at  very  acute 
angles;  the  resulting  trunks  uniting  until  the  tube  terminates  as 
a  papillary  duct. 

The  tubes  are  lined  with  epithelia;  and  these  cell  elements  con- 
stitute the  parenchyma  of  the  kidney.  The  lining  cells  are,  as  a 
rule,  of  the  columnar  variety.  Two  exceptions  are  presented,  one 
of  which  appears  in  the  flattened  cells  lining  Bowman's  capsule, 
and  the  other  in  a  like  form,  in  the  descending  limb  of  Henle's  loop. 
The  parenchyma  will  receive  attention  in  our  practical  work. 

BLOOD-VESSELS. 

The  vascular  arrangement  is  complex.  The  most  prominent 
and  essential  feature  is  afforded  in  the  existence  of  two  distinct 
capillary  plexuses. 

The  renal  artery,  as  already  described,  sends  branches  into  the 
substance  of  the  kidney.  These  pass  between  the  Malpighian 
pyramids,  and  in  the  cortical  columns.  These  arterial  trunks  arch 
over  the  bases  of  the  pyramids  of  Malpighii,  forming  the  arterial 
arcade.  From  these  arches  small  straight  branches  are  sent  out- 
ward toward  the  capsule  of  the  kidney,  occupying  a  position  mid- 
way between  the  pyramids  of  Ferrein,  in  the  labyrinths.  The  last 
are  the  interlobular  arteries.  During  their  course,  they  send  off 


THE   KIDNEY. 


125 


side  arterioles  which,  penetrate  the  capsule  of  the  Malpighian 
bodies.  Each  afferent  arteriole  breaks  up  into  a  capillary  plexus — 
the  tuft  or  glomerulus.  The  glomerulus  does  not  entirely  fill  the 


FIG.  87.— DIAGRAM  SHOWING  THE  ARRANGEMENT  OF  BLOOD-VESSELS  IN  THE  KIDNEY.    After 

Ludwig. 

capsule,  so  that  a  space  remains  between  the  spherical  mass  of 
capillaries  and  the  flattened  cells  lining  the  body.  The  glomeruli 
are  enveloped  with  a  single  layer  of  flattened  epithelial  cells. 


126  PRACTICAL    MICROSCOPY. 

The  blood  escapes  from  the  glomerulus  by  one  or  two  efferent 
arterioles  which  emerge  from  the  capsule  close  to  the  afferent  ves- 
sel. The  latter  is  the  more  noticeable,  as  it  is  usually  much  the 
largest.  The  efferent  arteriole  immediately  breaks  up  into  a  second 
capillary  plexus,  which  courses  between  the  uriniferous  tubules  of 
the  labyrinths  and  of  the  pyramids  of  Ferrein.  This  second  plexus 
also  descends  between  the  elements  of  the  pyramids  of  Malpighii. 
From  the  arteries  forming  the  arcade  another  set  of  branches — the 
arteriolcB  rectce — is  given  off;  which,  descending  into  the  Malpi- 
ghian  pyramids,  provides  another  and  direct  arterial  supply  to  the 
tubular  elements  by  elongate  capillary  loops. 

The  course  of  the  venous  trunks  is  not  unlike  that  pursued  by 
the  arteries.  Interlobular  veins  pass  into  a  venous  arcade;  the 
former  lying  in  the  cortical  labyrinths  parallel  with  and  close  to 
the  arteries.  In  the  medulla  the  venous  blood  is  collected  from 
the  capillaries  and  carried  to  the  bases  of  the  Malpighian  pyramids 
in  small  veins — venulse  recta?.  The  blood  from  the  cortical  inter- 
tubular  capillaries  is  collected  in  the  interlobular  veins. 

A  peculiar  vascular  arrangement  exists  just  beneath  the  capsule 
of  the  kidney,  consisting  of  scattered  venous  plexuses,  the  stars  of 
Verlieyen.  They  contain  blood  collected  from  contiguous  inter- 
tubular  capillaries  and  are  in  connection  with  the  summits  of  the 
interlobular  veins. 

From  what  has  been  said,  it  will  be  seen  that  the  cortical  and 
medullary  blood-supplies  are,  to  a  certain  extent,  independent  of 
one  another.  The  arteriolae  rectae  provide  a  vascular  supply  to  the 
elements  of  the  Malpighian  pyramids  even  after  many  of  the  glo- 
meruli  have  become  obliterated  by  disease. 

Nerve  and  lymphatic  elements  are  not  very  prominent  features 
in  sections  of  the  kidney.  Small  medullated  nerve  trunks  may  be 
easily  demonstrated  in  transverse  sections  of  the  cortex,  especially 
near  the  bases  of  the  medullary  pyramids,  where  they  will  be  seen, 
in  company  with  the  blood-vessels  of  the  arcades.  Lymph  chan- 
nels are  also  to  be  seen  in  the  vicinity  of  the  vessels  of  the  hilum, 
and  in  the  connective  tissue  of  the  capsule.  The  nervous  system 
of  the  kidney  would  prove  a  valuable  field  of  labor,  and  would  well 
repay  the  advanced  student's  patient  and  earnest  investigation. 

The  histology  of  the  kidney  will  be  better  comprehended  by  a 
reference  to  its  functioning.  The  separation  from  the  blood  of  a 
quantity  of  water,  together  with  certain  excrementitious  matters, 
is  effected,  partly  in  the  Malpighian  bodies,  and  partly  in  the 
tubules.  The  vascular  tuft — the  glomerulus — is  covered  with  a 


THE   KIDNEY.  127 

close  fitting  membrane  composed  of  flat  cells.  The  blood  in  this 
plexus  parts  with  a  certain  amount  of  its  water,  which  passes 
through  the  walls  of  the  capillaries  and  through  the  cells  covering 
them.  Whether  this  be  due  to  osmosis  or  to  some  selective  power 
of  the  cells  we  have  no  concern — suffice  it  that  certain  salts  after- 
ward appearing  in  the  urine  do  not  leave  the  blood  at  this  point. 
The  efferent  glomerular  arteriole,  it  will  be  remembered,  breaks 
into  a  second  capillary  plexus,  which  brings  the  blood  close  to  the 
walls  of  the  convoluted  tubules.  We  believe  that  the  cells  lining 
these  tubules  select  from  the  blood,  circulating  in  the  contiguous 
capillaries,  such  effete  materials  as  escaped  elimination  from  the 
glomeruli.  Moreover,  that  some  of  the  water,  together  with  serum 
albumin,  which  escaped  in  the  first  instance  and  entered  the  prox- 
imal convoluted  tubules,  is  here  returned  to  the  blood  by  the  inter- 
vention of  the  same  tubular  lining  cells  which  excrete  the  salts. 
That  in  the  cells  of  these  tubules  there  exist  currents  in  opposite 
direction — one  from  the  intertubular  capillaries  into  the  proximal 
part  of  the  tubule;  and  one  from  the  dilute  urine  in  the  tubule 
into  the  capillaries.  AVithout  referring  to  any  further  work  on  the 
part  of  the  kidney,  I  wish  to  impress  this  part  of  the  structural 
scheme:  That  the  first  part  of  the  uriniferous  tubule  is  the  prom- 
inent excreting  part.  That  the  latter  portion  of  the  tubule — the 
portion  in  the  Malpighian  pyramids,  the  straight  tubule — is  for 
the  collection  and  drainage  of  the  urine  already  excreted.  And 
that  between  the  excreting  first  part  and  the  draining  second  part, 
there  exists  a  narrow  looped  tubule — the  loop  of  Henle.  The  effect 
of  this  narrowing  and  tortuosity  of  the  tubule  will  be  to  present  a 
resistance  to  the  outflow  of  urine  from  the  proximal  portion  of  the 
tubule.  The  dilute  urine,  excreted  in  the  Malpighian  bodies,  is 
held  back  for  a  while  in  the  proximal  convoluted,  and  time  given 
for  the  completion  and  perfection  of  the  excretory  processes  by  the 
tubular  parenchyma. 

PRACTICAL  DEMONSTRATION. 

The  human  kidney  is  rarely  found  in  a  perfectly  normal  condi- 
tion. The  demonstration  can  be  made  from  the  kidney  of  the  pig, 
except  as  regards  certain  features.  The  medullary  pyramids  do 
not  exist  in  the  domestic  animals,  and  the  parenchyma  presents 
very  essential  differences  from  the  cells  of  the  human  kidney. 
Still,  very  much  can  be  learned  from  the  organ  of  the  pig,  dog,  and 
rabbit.  The  tissue  should  be  divided  so  as  to  permit  sections  to  be 
made  parallel  with  the  medulla,  and  to  include  both  it  and  the 
cortex.  The  hardening  is  best  by  Miiller's  fluid.  Small  pieces 
hardened  quickly  in  strong  alcohol,  however,  stain  very  finely  with 


128 


PRACTICAL    MICROSCOPY. 


hema.  and  eosin.  Very  pleasing  differentiation  may  also  be  secured 
by  staining  slowly  in  weak  borax-carmine,  clearing  with  glycerin, 
and  mounting  in  the  same  medium. 

HUMAN   KIDNEY.     SECTION   PARALLEL   WITH   MAL- 
PIGHIAN  PYRAMID.     STAINED  WITH   H^EMA.  AND 

EOSIN. 

(Fig.  88.) 
OBSERVE : 
(Naked  eye.) 

1.  The  thickness  of  the  cortex,  and  its  granular  appear- 
ance as  compared  with  the  medullary  portion. 


FIG.  88.— SECTION  OP  HUMAN  KIDNEY,  cur  PARALLEL,  TO  THE  PYRAMIDS  OF  FERREIN.    SHOW* 
ING  THE  CORTEX  AND  PART  OF  A  MALPIGHIAN  PYRAMID.     X  30. 

A,  A.    Capsule  of  kidney. 

B,  B.    Pyramids  of  Ferrein. 

C,  C.    Cortical  labyrinths. 

D,  D.    Malpighian  bodies.    Many  of  the  glomeruli  drop  out  in  the  course  of  preparation, 
and  such  empty  capsules  of  Bowman  appear  as  light  circular  spots. 

E,  E.    Interlobular  arteries.  F,  F.    Boundary  region. 
G,  G.    Transverse  sections  of  vessels  of  the  arcades. 

H .    Base  of  a  Malpighian  pyramid. 


THE   KIDNEY.  129 

2.  The  "  markings  of  the  cortex."  These  consist  of  alternat- 
ing light  and  dark  lines,  radiating  from  the  bases  of  the  Malpighian 
pyramids.     The  lighter  masses  consist  largely  of  collecting  tubes, 
together  with  ascending  limbs  of  Henle's  looped  tubes — otherwise 
called  medullary  radii.     Between  these  lighter  areas  the  dark 
labyrinths  appear;  in  which,  by  careful  attention,  the  Malpighian 
bodies  may  be  made  out  as  minute  red  dots, 

3.  A  region  just  outside  the  medullary  pyramids — not  as  well 
marked  as  the  outer  cortex,  in  which  few  Malpighian  bodies  pre- 
sent—the boundary  region. 

4.  The  finely  striated  medullary  or  Malpighian  pyramids. 
(The  section  will  usually  include  portions  of  two  of  the  last.) 

5.  That  the  bases  of  the  pyramids  do  not  appear  as  a  sharply- 
defined  line,  but  fade  into  the  boundary  region;  while  the  union  of 
the  latter  with  the  cortex  proper  is  equally  ill-defined. 

(L.)     Fig.  88. 

1.  The  cortical  labyrinths,  in  which  search  for — 

(a)  Portions  of  the  interlobular  arteries,  together  with  the 
smaller  twigs  of  the  arterial  arcade. 

(b)  The  Malpighian  bodies.     (The  tuft  or  glomerulus  which, 
with  this  power,  appears  as  a  granular  mass,  is  wanting  in  numer- 
ous places — as  indicated  by  the  empty  capsules.) 

(o)  The  remaining  area  occupied  largely  by  the  convoluted 
tubes,  proximal  and  distal. 

2.  The  pyramids  of  Ferrein.     (Observe  that,  as  they  pass 
into  the  pyramids  of  Malpighii,  they  are  well  defined,  but  that  they 
are  lost  as  they  approach  the  region  of  the  capsule  of  the  organ.) 

(H.)     Fig.  89. 

1.  A  Malpighian  body.  (Select,  after  searching  several  fields, 
a  specimen  which  shows  either  the  afferent  or  efferent  vessel  of 
the  glomerulus.  It  will  be  very  difficult  to  find  a  capsule  con- 
nected with  the  neck  of  a  proximal  convoluted  tube,  as  they 
rarely  happen  to  be  so  sectioned.  You  may  indeed  be  obliged  to 
examine  a  dozen  slides  before  you  succeed.)  Note — 

(a)  The  capsule  (of  Bowman  or  of  Miiller).    (Observe  its  thick- 
ness, as  this  becomes  important  in  connection  with  the  pathology 
of  the  kidney.) 

(b)  The  flattened  cells,  lining  the  capsule.     (Many  of  them 
will  have  become  detached  in  the  preparation  of  the  section.) 

(c)  The  glomerulus.     (The  great  number  of  nuclei  obscures: 
the  loops  of  capillaries.     Eemember  that  the  nuclei  belong  partly 

9 


130 


PRACTICAL    MICROSCOPY. 


to  the  vessels,  and  partly  to  the  flattened  cells  covering  the  glomer- 
ulus.  Endeavor  to  find  transversely  divided  loops  of  the  ves- 
sels, showing  blood  within.) 

(d)  That  the  glomerulus  does  not,  entirely,  fill  the  capsule. 

(e)  That  the  tuft  is  frequently  divided. 

(/)  That  the  tuft  is  usually  in  contact  with  the  capsule 
at  some  one  point,  where  search  may  be  made  for 


FIG.  89.— PART  OP  THE  CORTEX  OP  HUMAN  KIDNEY.    HIGH  POWER.    SAME  SPECIMEN  AS  FIG. 

88.     X  400. 

A.  Ascending  limb  of  Henle's  loop. 

B.  Collecting  tubule— longitudinal  section. 

C.  Collecting  tubule.    The  upper  part  of  the  tube  is  not  sectioned,  but  shows  the  attached 
bases  of  the  lining  cells  ;  and  thus  simulates  pavement  epithelium.    A,  B,  and  C  are  in  a 
pyramid  of  Ferrein. 

D.  Capsule  of  a  Malpighian  body.    The  emecging  tubule  is  not  shown,  as  the  body  is  in 
T.  S. 

E.  Flattened  lining  cells  of  D. 

F.  Glomerulus. 

0.  Efferent  arterioles. 
H.    Afferent  arteriole. 

1.  Convoluted  tubules. 

J.    Ascending  limb  of  Henle. 
K.    Intertubular  capillaries. 

(g)  The  afferent  and  efferent  arterioles.     (The  afferent  is 
more  frequently  demonstrable;  and  may  be  differentiated  by  its 


THE    KIDNEY.  131 

large  size  and  the  connection,  which  can  often  be  traced,  with  the 
interlobular  artery.) 

2.  Convoluted  tubules.       (The  convoluted  tubes  found  just 
beneath  the  capsule  of  the  kidney  generally  belong  to  the  distal 
variety;  and  they  are  not  as  favorable  specimens  as  the  deeper 
proximal  portions,  on   account   of  the  crowding  of   the  tubular 
elements  in  the  outer  cortical  regions.     Select  a  transverse  section 
and  observe :) 

(a)  The  thin  membrana  propria,  or  wall  of  the  tube.     (It 
does  not  appear  to  be  made  up  of  fibrillated  connective  tissue;  but, 
rather,  presents  a  homogeneous  structure.     Nuclei,  however,  may 
occasionally  be  seen,  which  apparently  belong  to  this  tissue.) 

(b)  The  peculiar  lining  cells.     (They  are  unlike  any  other 
parenchymatous  elements  found  in  the  body.     Note  that,  while 
they  are  evidently  of  the  columnar  or  cylindrical  type,  they  differ 
greatly  in  form  and  size.     The  protoplasm  is  hazy,  granular,  and  fre- 
quently striated.    They  take  a  dirty  brick-red  hue  from  the  eosin.) 

(c)  The  lumen.     (Compared  with  the  diameter  of  the  tube- 
wall,  the  lumen  is  very  small,  and  presents  a  stellate  figure.     The 
urine,  in  passing  through  the  tubule,  is,  consequently,  brought  in 
contact  with  a  very  considerable  portion  of  the  parenchymatous 
lining.) 

3.  The  large  proportion  of  the  cortical  area  occupied  by 
the  convoluted  tubules,  and  the  exceedingly  small  amount  of 
intertubular  connective  tissue. 

4.  The  intertubular  capillaries.      (These    are    exceedingly 
small,  and  difficult  of  demonstration  unless  they  be  filled  with 
blood.     The  nuclei  of  the  endothelial  wall   are  frequently  seen. 
The  cells  of  the  convoluted  tubules  are  not  infrequently  detached 
from  the  membrana  propria,   and  the  space  so  formed  may  be 
mistaken   by   tke  careless  observer   for  longitudinal  sections   of 
capillaries.     These  vessels  are  much  better  seen   in  an  injected 
kidney;  although  if  an  organ  be  selected  containing  considerable 
blood,  and  the  corpuscular  elements  have  their  color  preserved  (as 
in  bichromate  hardening),  the  vessels  will  be  easily  demonstrated.) 

5.  Ascending  limb  of  Henle's  loops,  in  the  cortical  lab}- 
rinths.     (The  general  course  of  these  tubules  is  confined  to  the 
pyramids  of  Malpighii  and  Ferrein;  but  occasionally  one  of  them 
may  be  seen  passing  in  a  tortuous  course  toward  the  outer  cortex, 
running  between  the  proximal  convoluted  elements.     They  are 
easily  recognized  by  their  small  size  and  relatively  large  lumen. 
They  are  lined  with  short  columnar  or  cuboid  cells,  which  stain 
deeply  blue  with  the  ha3ma.) 


132  PRACTICAL    MICROSCOPY. 

6.  The  pyramids  of  Ferrein. 

(a)  Collecting  tubes.  (These  will  be  generally  recognized  by 
their  large  size  and  the  blue  color  of  the  staining.     They  are  lined 
with  columnar  cells,  which  are  hexagonal  in  transverse  section; 
and  this  gives  an  appearance  of  pavement  epithelium,  when  they 
are  seen  from  above   or  below.     Endeavor  to  find  a  tube  split 
through  the  centre,  longitudinally  and  note  the  typical  columnar 
cells,  as  they  project  inward  from  the  membrana  propria,  toward 
the  now  open  lumen.) 

(b)  The    spiral  tubules.      (These    resemble  somewhat    the 
convoluted  tubules,  especially  as  their  cells  take  much  the  same 


FIG.  90  —MEDULLARY  PORTION  OF  SPECIMEN  SHOWN  IN  FIG.  88.    x  400. 

A.  Collecting  tubule  in  L.  S. 

B.  Collecting  tubule  from  above,  showing  attached  bases  of  lining  cells. 

C.  Collecting  tubule  presenting  different  appearance  of  lining  cells,  according  to  mode  of 
section. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Same  as  last.    The  upper  end  of  the  tubule  not  sectioned. 

F.  Descending  limb  of  Henle's  loop.    Below  may  be  seen  the  loop  and  ascending  limb. 

G.  Oblique  section  of  large  collecting  tubule. 

H.    Basal, -attached  extremities  of  cells  lining  a  large  collecting  tubule. 
I.    Intertubular  capillaries. 

dirty  red  color.     The  cells,  however,  plainly  columnar,  are  large 
and  hexagonal  in  transverse  section.     The  lumen  is  small.) 


THE   KIDNEY.  133 

(c)  Ascending  limbs  of  Henle's  loop.      (These  are  small 
tubes  and  have  already  been  described.) 

(d)  The  intertubular    capillaries.      (Inasmuch  as,  in  the 
specimen  under  consideration,  the   vessels   of  the  pyramids  are 
mostly  in  transverse  section,  they  are  not  readily  made  out.     Es- 
pecially is  this  true  if  the  blood -corpuscles  have  their  color  dis- 
charged.) 

7.  Elements  of  the  medullary  portion.     Fig.  90. 
(a)  Collecting1  tubes.     (These  tubes  constitute  a  large  pro- 
portion of  the  medulla  of  the  organ.     They  have  been  already  de- 


~FiG.  91.— TRANSVERSE  SECTION  OF  PYRAMID  OF  MALPIGHII.    SAME  TISSUE  AS  SHOWN  IN 
FIG.  88.    Stained  with  Haema.  and  Eosin.     X  400. 

A.  Group  of  intertubular  blood-vessels. 

B.  Collecting — straight— tubules. 

C.  Descending  limb  of  Henle's  loop. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Principal— collecting— tubule. 

F.  Principal  tubule.    Lower  portion  near  the  papillary  duct. 

The  ring  of  cells  will  be  seen  detached  from  the  membrana  propria  in  some  instances. 
This  is  due  to  contraction  of  the  tissue  during  the  hardening. 

scribed.     As  the  apex  of  the  Malpighian  pyramid  is  approached, 
and  the  straight  unite  to  form  the  principal  collecting  tubes,  these 


134  PRACTICAL    MICROSCOPY. 

again  uniting  to  form  the  papillary  ducts,  the  lining  cells  will  be 
seen  to  get  shorter,  and  the  lumina  larger.) 

(b)  Spiral  tubes.  (These  can  be,  in  many  instances,  followed 
down  from  the  pyramids  of  Ferrein;  and  examples  are  frequently 
seen  very  near  the  pelvis  of  the  kidney  in  the  cortical  columns.) 

(6i)  Descending  limbs  of  Henle's  loop.  (These  tubes  are 
the  most  difficult  of  all  the  tubuli  uriniferi  to  demonstrate.  The 
section  must  be  very  thin,  and,  even  then,  they  may  be  mistaken 
for  blood-capillaries.  Their  peculiar  feature  consists  in  the  wavy 
lumen,  which  is  produced  by  the  alternate  disposition  of  the  lining 
cells.) 

(d)  Loop  of  Henle.     (The  loops  will  be  recognized  by  the 
curving  of  the  tube.     They  are  lined  with  short  columnar  cells 
which  are  sharply  brought  out  by  the  hagma.     On  account  of  their 
course  but  few  complete  sections  are  seen.) 

(e)  Ascending  limbs.     (Conveniently  traced  from  the  loop.) 
(/)  Intertubular  blood-vessels.     (Do  not  mistake  tubules 

containing  blood,  for  capillaries.  The  human  kidney  is  rarely 
absolutely  normal;  and  blood  is  frequently  found  outside  the 
proper  channels.  The  vessels  will  be  differentiated  by  the  histology 
of  their  walls.  Quite  a  number  of  venules  will  be  seen  running 
in  groups  in  the  medulla — the  venulce  rectce. 

8.  The  same  elements  as  in  7  (shown  in  a  transverse  section 
of  the  middle  of  a  Malpighian  pyramid,  Fig.  91). 


GENITO-UEINAKY    ORGANS. 


EPITHELIUM  OF  THE  GENITOURINARY 

TRACT.     URETER,  BLADDER,  UTERUS, 

VAGINA,  ETC. 

The  lining  membrane  of  the  genito-urinary  apparatus  is  of  in- 
terest to  the  medical  man;  particularly  in  connection  with  diseases 
whose  diagnosis  may  be  largely  determined  by  a  microscopical  ex- 
amination of  urinary  deposits. 

In  the  preparation  of  this  subject,  I  have  confined  myself, 
rather  closely,  to  the  consideration  of  such  portions  of  the  lining 
of  the  genito-urinary  tract  as  may  be  recognized  and  differentiated, 
as  they  occur  in  urine  and  other  fluid  discharges.  The  limit  pre- 
scribed for  these  pages  will  permit  little  beyond  this. 

It  is  not  always  possible  to  determine  the  origin  of  detached 
cells,  for  two  reasons,  viz. :  First,  certain  widely-separated  portions 
are  very  similarly  cell-covered;  and,  secondly,  cells  which  are  the 
result  of  proliferation  accompanying  diseased  processes  are  quite 
frequently  unlike  the  original  type.  Still,  certain  portions  of  the 
genito-urinary  apparatus  have  a  distinctly  characteristic  epithelium; 
and  to  such  will  our  present  notice  be  directed. 

PRACTICAL  DEMONSTRATION. 

From  the  body  of  a  (preferably  young)  human  female,  as  soon 
as  possible  after  death,  remove  half-inch  cubes  of  the  organs  re- 
quired, observing  that  the  lining  is  included.  The  outer  portions 
are  of  very  little  moment  comparatively.  Secure  pieces  from  the 
os,  cervix  and  fundus  of  the  uterus,  the  base  of  the  bladder,  the 
wall  of  the  vagina  near  the  cul-de-sac,  the  ureters,  and  the  pelvis 
of  the  kidney. 

We  desire  to  prepare  the  tissue  so  as  to  keep  the  original  form 
of  cell  elements — to  avoid  contraction;  and  the  M  tiller  process 
will  accomplish  this  perfectly.  Allow  the  pieces  to  remain  for  two 
weeks  in  the  bichromate  solution,  with  an  occasional  change.  Com- 
plete the  hardening  in  Nos.  3, 2,  and  1  alcohol,  as  usual.  Infiltrate 
with  celloidin  or  bayberry  tallow,  and  let  the  sections  be  vertical  to 
the  mucous  surface.  The  tissues  should  not  be  handled  with  the 
fingers,  otherwise  the  epithelial  lining  ceils  will  be  detached.  Stain 
with  haema.  and  eosin ;  mount  in  dammar. 


136 


PRACTICAL    MICROSCOPY. 


UTERUS  AND  VAGINA  OF  THE  HUMAN  FEMALE  AT 

PUBERTY. 

VERTICAL   DEXTRO-SINISTRAL    SECTION  OF   THE    RIGHT   LIP  OF    THE 

OS,  AND  INCLUDING  PART  OF  THE  VAGINAL  CUL-DE-SAC. 
OBSERVE: 


1.  The  outline  of  the  section.     (Commencing  at  D,  Fig.  92, 
which  is  placed  in  the  internal  OS,  followed  downward,  out  upon 


FIG.  92. — VERTICAL  DEXTRO-SINISTRAL  SECTION  OF  THE  RIGHT-HAND  SIDE  OF  THE  Os  UTERI. 
SHOWING  THE  INTERNAL  Os,  THE  EXTERNAL  Os,  THE  VAGINAL  CUL-DE-SAC,  AND  THE  UPPER 
PORTION  OF  THE  VAGINAL  WALL.  X  60. 

A.  The  letter  is  placed  in  the  internal  os. 

B.  Vaginal  cul-de-sac. 

C.  Vaginal  wall. 

D.  Columnar  epithelium  of  the  internal  os.    In  the  upper  portion  the  tubular  glands  are 
well  seen. 

E.  Stratified  epithelium  of  the  vaginal  lining. 

F.  Change  at  the  external  os  from  stratified  flattened,  to  columnar  epithelium. 

the  external  os,  curve  upward,  reaching,  at  B,  the  vaginal  cul- 
de-sac.     Descend  along  the  right  vaginal  wall.) 

2.  The  irregular  surface   of  the   internal  uterine  wall. 
(Caused  by  longitudinal  section  of   the  glandulae  uterinse  or  g. 


UTERUS    AXD    VAGINA. 

utriculares,  branched  tubular  glands.  These  are  increased  in  depth 
during  pregnancy,  and  are  most  prominent  in  the  lower  portion  of 
the  organ.) 

3.  The  epithelium,     (a)  The  deeply  stained  layer  lining 
the  vagina,  cul-de-sac,  and  external  os.    (b)  The  wavy  course 
of  a  as  it  covers  the  irregularly  formed  and  often  imperfect  papillae 
of  the  mucosa.     (c)  The  lighter  appearance  of  the  lining  of  the 
internal  os.     (d)  Projection  of  the  last  into  the  glands,     (e) 
The  sharp  line  of  separation  between  the  deeply  stained  lining 
common  to  the  vagina  and  the  lighter  lining  of  the  uterus  at  the 
external  os  (Fig.  92,  F). 

4.  The  mucosa  of  the  uterus.     (There  are  no  sharply  defined 
regions  in  the  genito-urinary  tract  corresponding  to  the  mucosa 
and  submucosa  of  typical  mucous  membranes.     The  arrangement 
generaly  is:  1,  an  epithelial  lining;  2,  a  subepithelial  structure, 
consisting  of  a  more  or  less  prominent  or   abundant   plexus    of 
capillaries  supported  by  delicate  connective  tissue,  and  which  cor- 
responds to  the  mucosa  of  typical  structures;  3,  loose  connective 
tissue,  with  more  or  less  muscular  tissue,  containing  larger  vessels, 
not  separated  from  the  mucosa  by  any  well-defined  line  or  muscu- 
laris  mucosse,  which  represents  the  submucosa;  5,  the  muscular 
walls  proper,  consisting  of  layers  in  different  directions,  frequently 
irregularly  disposed  and  seldom  in  distinct  fascicula?.) 

5.  The  mucosa  of  the  vagina  (less  distinct  than  that  of  the 
uterus). 

6.  The  uterine  and  vaginal  walls  (consisting  largely  of  in- 
voluntary muscular  fibrils,  recognized  by  the  elongate  and  deeply 
stained  nuclei,  and  containing  numerous  thick-walled  arteries  and 
irregular  lymph  spaces). 

(H.) 

7.  The  uterine  epithelium  (Fig.  93).     (a)  That  it  consists  of  a 
single  layer  of  cells.     (7>)  That  the  cells  are  columnar,  not  cyl- 
indrical,    (c)  The  cells  in  transverse  section  are  polygonal,      (d) 
They  are  ciliated.     (This  demonstration  is  not  always  made;  but 
if  the  section  has  been  properly  prepared  from  uninjured  tissue,  the 
cilia  will  be  seen  without  difficuty,  and  especially  in  the  depres- 
sions where  they  are  somewhat  protected.)     (e)  The  cell  body  and 
nucleus.     (Note  the  elongate,  clear,  free  portion  and  the  frequent 
curving  of  the  whole.     Near  the  attached  extremities,  which  often 
appear  pointed,  note  the  small  deeply  stained  nuclei.)     (/)  The 
large  mucous  cells.     (These  singular  cells  appear  scattered  be- 
tween the  cylinders,  with  a  clear  bulging  body,  often  six  times  the 


138 


PRACTICAL    MICROSCOPY. 


breadth  of  the  ordinary  elements.)     (g)  The  absence  of  any  spe- 
cial basement  membrane. 

8.  The  abrupt  transition  from  columnar  to  flattened  cells 
in  the  epithelium  of  the  external  os.  (a)  The  shortening  of  the 
columnar  cells  as  the  point  of  change  is  approached.  (Sections 
must  be  examined  until  one  is  found  showing  this  point  well.  The 
illustration  (Fig.  93)  is  not  exaggerated,  and  a  properly  cut  and 
selected  specimen  must  exhibit  clearly  the  last  columnar  and  the. 


FIG.  93. — EXTERNAL  Os  OF  FIG.  92.    MORE  HIGHLY  MAGNIFIED.     X  400. 

A.  Muscular  tissue  of  the  os  uteri,  with  numerous  blood-vessels. 

B.  Capillary  plexuses  of  sub-epithelial  tissue — mucosa. 

C.  Ciliated  columnar  cells  covering  the  os. 

D.  Vacuolated  cells. 

E.  Shortening  of  the  columnar  cells  prepartory  to 

F.  Change  from  typical  uterine  epithelia— ciliated  columnar  cells— to  flattened,  stratified 
cells. 

G.  Papillary  structure  of  the  mucosa  of  the  external  os,  after  the  change  of  epithelium. 

adjoining  flattened  cell.  I  know  of  no  location  in  the  human  body 
where  the  change  in  form  of  cell  covering  approaches  this  in 
abruptness.) 

9.  The  vaginal  epithelium  (Figs.  93  and  94).     (a)  That  it  is 
of  the  stratified  variety,     (b)  The  deepest  line  of  cells  follow- 


UTEKUS   AND   VAGINA. 


139 


ing  the  sinuous  line  formed  by  sectioning  the  papillary  mucosa. 
(c)  That  the  cells  are  more  or  less  flattened,  (cl)  That  their 
edges,  excepting  those  of  the  surface,  are  serrated.  (The  union 
is  by  a  cement  between  the  interdigitating  cell  bodies.)  (e)  The 
change  in  form  as  the  surface  is  approached.  (/)  The  sur- 
face cells.  (These  are  very  much  flattened,  and  so  fused  as  to  re- 
semble, in  longitudinal  section,  fibres.)  (g)  Detached  surface 
cells.  (At  H,  Fig.  94,  these  are  shown  in  plan,  having  been  torn 
oil;  those  intact  are,  of  course,  seen  in  profile.  Fig.  97  represents 


FIG.  94.— VERTICAL  SECTION  OP  THE  VAGINAL  LINING  AT  PUBERTY.    Stained  with  Hsema. 

and  Eosih.     x  400. 

A.  Sub-epithelial  capillary  plexus. 

B.  Papillary  arrangement  of  the  mucosa. 

C.  Large  blood-vessels  in  the  submucosa. 

D.  Muscular  wall  of  vagina. 

E.  Deep  cells  of  the  lining  epithelium. 

F.  Middle  strata  of  lining  stellate  cells. 

G.  Surface  cells  in  profile. 

H.    Surface  cells  in  plan— detached. 

the  same  elements  as  they  generally  appear  in  a  film  of  urine.) 
(li)  The  nuclei,  evenly  granular,  usually  larger  than  a  red  blood- 
corpuscle,  (i)  Vacuolated  cells. 

30.  The  subepithelial  vaginal  structures,     (a)   The  large 
and  abundant  capillaries  of  the  mucosa.     (b)  The  submucosa> 


140 


PRACTICAL    MICROSCOPY. 


not  clearly  separated  from  the  superior  coat,  but  easily  recognized 
by  the  large  vessels  and  the  abundant  connective  tissue,  (c)  The 
muscular  vaginal  wall.  (Here  the  muscular  bundles  are  much 
better  defined  than  in  the  uterine  walls.) 

PELVIS   OF   THE   KIDNEY  AND   URETER. 

TRANSVERSE  SECTION  OF  THE  URETER  NEAR  THE  PELVIS  -OF  THE 
KIDNEY,  AND  DETACHED  CELLS  FROM  THE  EPITHELIAL  LIN- 
ING OF  PELVIS.  (Figs.  95  and  97.) 

(The  arrangement  and  form  of  the  cells  lining  the  pelvis  of  the 
kidney  and  the  ureters  are  precisely  similar,  and  so  far  Fig.  95 
will  represent  both.) 


FIG.  95.— TRANSVERSE  SECTION  OP  THE  URETER,  NEAR  THE  PELVIS  OP  THE  KIDNEY.    Stained 
with  Hsema.  and  Eosin.     X  400. 

A.  Rich  capillary  plexus  of  the  mucosa. 

B.  Internal  circular  muscular  coat. 

C.  External  longitudinal  muscular  bundles. 

D.  Large  vessels  of  the  areolar  adventitia. 

E.  Deep  layer  of  somewhat  cubical  cells. 

F.  "  Tailed  cells  "  of  the  middle  epithelial  lining. 

G.  Surface  cells  in  profile. 

H.    Surface  cells  in  plan — detached. 


THE    URLfrAKY    BLADDER.  141 

OBSERVE: 

(L.) 

1.  The  relative  thickness  of  the  epithelium. 

2.  The  narrow  mucosa. 

3.  The  internal  circular  muscular  belting1. 

4.  The  transversely  divided  bundles  of  the  external  longi- 
tudinal muscular  layer. 

5.  The  large  arteries  between  the  muscular  bundles. 

6.  Adipose  tissue,  more  or  less  abundant  in  the  loose  cellular 
tissue  surrounding  these  canals.     (This  element  will  afford  a  prom- 
inent feature  of  a  section  of  the  pelvis  of  the  kidney,  while  the 
muscular  tissue  will  be  seen  to  a  limited  extent  only.) 

(H.) 

7.  The  epithelium,     (a)  That  it  is  of  the  stratified  type, 
though  poorly  demonstrated,     (b)  The  broad  basal  attachment  of 
the  deep  cells,     (c)  The  elongate  form  of  the  cells  generally. 
(d)  That  the  borders  are  smooth  and  closely  adherent,  unlike 
those  of  the  vagina,     (e)  The  more  flattened  surface  cells.     (/) 
The  outline  of  the  last,  as  seen  in  the  detached  specimens,     (g) 
The  very  large  and  finely  granular  nuclei.     (These  cells  con- 
tain peculiarly  large  nuclei,  as  compared  with  the  size  of  the  body. 
The  deeper  examples  present  tapering  prolongations,  generally  at 
one  end  only,  and  are  hence  called  "  tailed  cells/'     They  will  not 
be  confounded  with  similarly  shaped,  though  much  larger  cells 
from  the  bladder.     The  surface  elements,  while  sometimes  nearly 
circular,  generally  present  one  or  two  incurvations  of  the  periphery, 
indicating  their  connection  with  the  neighboring  cells.      These 
peculiarities  are  best  exhibited  in  Fig.  97.) 

8.  (Review  the  objects  previously  examined  with  low  power.) 

THE  URINARY   BLADDER. 

VERTICAL  SECTION"  OF  INNER  PORTION  OF  WALL.     (Fig.  96.) 
OBSERVE  : 

(L.) 

1.  The  epithelial  lining,  (a)  That  it  is  formed  after  the 
stratified  type,  (b)  That,  as  compared  with  other  previously 
studied  portions  of  the  genito-urinary  tract,  the  epithelium  is 
thin. 


142  PRACTICAL    MICROSCOPY. 

2.  The  thin  mucosa  and  its  small  capillary  supply. 

3.  The  dense  muscular  portion,  not  arranged  in  bundles. 

(H.) 

4.  The  epithelium,  (a)  The  magnitude  of  the  cells,  (b)  The 
broad-based  cells  without  any  special  basement  membrane. 


FIG.  96.— VERTICAL  SECTION  OF  THE  LINING  PORTION  OP  THE  BLADDER  (MALE)  BEHIND  THE 

TRIGONE. 
Stained  with  Haema.  and  Eosin.     x  400. 

A.  Connective  tissue  of  sub-epithelial  region,  containing  large  amount  of  muscular  fibre. 

B.  Scant  capillary  supply  of  sub-epithelial  region. 

C.  Muscular  wall  of  bladder. 

D.  Large  basement  cells  of  the  epithelial  lining. 

E.  Middle  region  of  lining. 

F.  Detached  surface  cells,  showing  processes  beneath. 

G.  Thin  surface  cells  in  profile. 

H.    Squamous  surface  cells,  seen  detached,  in  plan. 
I.    Vacuolated  cells. 

(c)  The  three  regions,  viz.,  basal,  middle,  and  superficial. 
(cl)  The  form  of  the  middle  cells  ;  not  unlike  in  outline,  though 
larger,  those  of  the  corresponding  region  in  the  ureter.  (This  is 
best  shown  in  Fig.  97.)  (e)  The  large,  scaly,  and  often  fused  sur- 


THE   URINAKY   BLADDEK. 


143 


face  epithelia.  (Note  that  while  these,  when  seen  in  plan,  all 
appear  flat,  it  is  only  those  of  the  extreme  surface  that  are  simple 
scales;  the  less  superficial  examples  show,  when  viewed  in  profile, 


PIG.  97. — CELLS  FROM  GENITOURINARY  TRACT.    ISOLATED  BY  TEASING,  AS  IN  TEXT,    x  400. 

A.  Surface  bladder  cells. 

B.  The  same  seen  partly  in  profile. 

C.  C.    Bladder  cells  from  deeper  layers. 

D.  Surface  vaginal  cells. 

E.  Vaginal  cells  from  deeper  layers. 

F.  Superficial  cells  from  pelvis  of  the  kidney  or  upper  ureter. 

G.  H.    From  the  same  as  F— deep  layers.    "  Tailed  cells."    G.  is  the  more  usual  form. 
I.    Ciliated  vaginal  cells. 

J,  K.    Cells  from  collecting  tubules  of  the  kidney. 

L.    Pus-corpuscles.    Not  stained. 

M.    Red  blood-corpuscles. 

L  and  M  are  introduced  as  measurement  standards  of  comparison. 


prolongations  from  the  under  surface,  by  means  of  which 
union  is  effected  with  the  deeper  cells.)  (/)  Vacuolated  cells. 
(These  vacuolations  do  not  occur  in  the  basal  layer.) 


144  PRACTICAL    MICROSCOPY. 


THE  OVARY. 

The  ovary  consists  of  a  stroma  or  ground  substance  of  connec- 
tive and  smooth  muscular  tissue,  in  which  are  scattered  various, 
sized  spherical  bodies  or  Graafian  follicles. 

The  stroma  is  divided  into  three  layers  or  regions,  which  are 
not  very  sharply  differentiated. 

The  ovary  is  covered  upon  its  free  surface  with  a  single  layer  of 
cells  which  in  early  life  are  cylindrical,  becoming  shortened  with 
advancing  age  until  after  the  -menopause 9  when  only  flattened  scales 
can  be  demonstrated. 

Immediately  beneath  the  epithelium  a  thin  layer  of  fibrous  tis- 
sue presents,  with  a  free  admixture  of  smooth  muscle  cells,  and  is 
termed  the  tunica  albuginea. 

The  cortex  proper,  or  second  layer,  is  distinguished  by  the 
Graafian  follicles,  which  will  be  described  later. 

The  central  portion  of  the  organ,  the  zona  vasculosa,  is  largely 
occupied  by  thick-walled  blood-vessels,  among  which  the  extremely 
tortuous  arteries  are  specially  evident.  Occasionally  may  be  seen, 
in  this  region  somewhat  ovoid  nodules  in  varying  degrees  of  retro- 
grade change — the  copora  lutea.  They  present  the  phenomena  re- 
sulting from  the  maturation  of  the  follicle  during  menstruation. 
The  accompanying  illustration  was  drawn  from  a  corpus  luteurn 
which  had  formed  in  the  site  of  a  Graafian  follicle,  the  contents  of 
which  had  escaped  at  some  menstrual  epoch,  and  been  followed  ~by 
impregnation. 

PRACTICAL     DEMONSTRATION. 

The  ovary  of  a  young  animal  is  to  be  preferred.  If  the  organ 
cannot  be  obtained  from  the  human  subject,  the  female  of  almost 
any  domestic  animal  will  provide  an  excellent  demonstration  for 
the  histological  elements.  Let  the  tissue  be  hardened  with  strong 
alcohol,  and  sections  be  cut  vertically  to  the  free  surface  and  stained 
with  haema.  and  eosin.  The  sections  should  include  at  least  one- 
half  the  depth  of  the  organ,  so  as  to  exhibit  all  of  the  regions. 

SECTION   OF   THE  ADULT   HUMAN  OVARY.    (Fig.  98.) 
OBSERVE: 

(L.) 

1.  The  tunica  albuginea.  (Note  that  the  layer  is  not  of  uni- 
form thickness,  and  is  composed  largely  of  smooth  muscular  tissue^ 


THE    OVARY. 


145 


as  shown  by  the  numerous  elongate  nuclei.     Search  particularly 
for  and  note  the  character  of  the  epithelial  covering.) 

2.  The  cortical  layer,  containing  numerous  Graafian  follicles, 
and   possibly  a   corpus   luteum.     (Note   the   aggregation   of   the 
smaller  follicles  in  the  extreme  outer  portion  of  the  region.) 

3.  The  zona  vasculosa.     (Note  the  unusual  thickness  of  the 
vascular  walls  and  the  irregular  outline  of  section,  on  account  of 
their  tortuous  course.) 


FIG.  98.— SECTION  OP          OVARY  FROM  A  WOMAN  35  YEARS  OLD.    Stained  with  Haema.  and 

Eosin.     X  250. 

A.  Surface  of  the  ovary. 

B.  Muscular  stroma. 

C.  Large  tortuous,  thick-walled  arteries  of  the  central  portion  of  the  organ. 

D.  D.    Small  Graafian  follicles  of  the  superficial  zone 

E.  Larger  follicles  of  the  deeper  portion. 

F.  Membrana  propria  of  a  Graafian  follicle. 

G.  Membrana  granulosa  of  the  follicle.    The  line  leads  to  the  discus  proligerus* 
H.    An  ovum. 

I.    Germinal  vesicle. 

J.    Germinal  spot. 

K.    An  old  corpus  luteum. 

(H.) 

4.  The  Graafian  follicles,      (a)    Their  diameter,  varying- 
from  one-one-hundredth  to  one-one-thousandth  of  an  inch.     (5) 
10 


146  PRACTICAL    MICROSCOPY. 

The  membrana  propria.  (This  is  difficult  to  separate  from  the 
stroma  of  the  ovary  itself,  except  in  more  mature  follicles  than 
shown  in  the  section.)  (c)  The  membrana  granulosa.  (This, 
in  general,  appears  to  be  the  outer  layer  of  the  follicle,  on  account 
of  the  difficulty  of  separating  the  membrana  propria  from  the 
stroma  proper  of  the  ovary.  Note  that  it  is  composed,  in  the 
smaller  and  less  mature  follicles,  of  pavement  cells,  and  that  the 
cells  becomes  thicker  with  maturation,  until  columnar  cells  in 
single  layer  result.)  (d)  The  ova.  (These  are  contained  within 
the  follicles,  excepting  they  may  have  become  detached  during 
manipulation  of  the  section,  and  occupy  the  greater  area  of  the 
same.)  (e)  The  zona  pellucida  (the  thin  wall  of  the  ovum).  (/) 
The  discus  proligerus.  (This  will  be  recognized  as  a  mass  of 
polyhedral  cells,  connecting  the  ova  at  one  side  with  the  columnar 
cells  of  the  membrana  granulosa.  These  cells  will  proliferate  later 
in  the  development,  and  completely  inclose  the  ovum.)  (g]  The 
germinal  vesicle.  (Contained  within  the  ovum.  The  contents 
appear  granular;  it,  as  well  as  the  ovum,  is  fibrillated;  but  this 
demonstration  cannot  be  made  excepting  the  animal  be  killed  for 
the  purpose,  and  the  tissue  elements  fixed  before  changes,  which 
quickly  follow  death,  occur.)  (h)  The  germinal  spot.  (Appear- 
ing as  a  small  dot  within  the  germinal  vesicle.  The  ovum  presents 
the  characteristics  of  what  it  indeed  is — a  typical  cell,  with  wall, 
body,  nucleus,  and  nucleolus.) 

5.  The  corpus  luteum.  (The  example  shown  in  the  drawing, 
as  I  have  already  said,  was  developed  after  the  contents  of  the 
Graafian  follicle,  which  it  represents,  had  suffered  impregnation; 
and  it  has  arrived  at  the  later  stage  of  the  series  of  phenomena 
connected  with  its  development — the  stage  of  cicatrization.  The 
cicatricial  tissue,  to  which  the  letter  K  points,  indicates  the  re- 
mains of  the  membrana  granulosa.  Outside  is  seen  the  thickened 
membrana  propria,  while  among  the  contents  will  be  found  pig- 
ment-granules and  fat-globules,  imbedded  in  a  structureless,  gelat- 
inous stroma.  This  material  results  from  changes  in  the  clot  of 
blood  effused  after  the  escape  of  the  ovum.  I  do  not  tabulate 
these  elements,  as  it  is  extremely  improbable  that  the  student  will 
find  a  corpus  luteum  in  precisely  the  condition  of  the  one  repre- 
sented until  he  has  examined  a  large  number  of  specimens.) 


DEVELOPMENT   OF   THE   OVUM.  147 


DEVELOPMENT  OF  THE  OVUM. 

As  has  been  previously  shown,  the  ovary  is  covered  with  epi- 
thelium; and  singular  as  it  may  appear,  the  fifty  thousand  Graafian 
follicles,  which  it  is  estimated  are  developed  during  the  life  of  the 
human  female,  have  their  origin  in  these  cells. 

During  foetal  life,  this  surface  epithelium  undergoes  a  very 
rapid  proliferation,  and  chains  of  cells  are  imbedded  in  the  stroma 
of  the  ovary.  A  little  later  in  the  development,  separate  portions 
or  links  of  these  chains  are  cut  oif  by  the  ingrowth  of  the  stroma. 
The  little  groups  of  cells  thus  isolated  become  each  a  Graafian 
follicle. 

Scattered  among  the  columnar  cells,  larger,  more  nearly  spher- 
ical cells  are  also  found,  the  primordial  ova.  These  are  also  im- 
bedded in  the  substance,  and  one  at  least  will  always  be  found 
among  the  minute  collections  of  cells  which  have  been  isolated. 

In  the  process  of  development,  each  group  of  cells  becomes  a 
Graafian  follicle  with  its  contained  ovum,  the  columnar  cells  form- 
ing the  wall  proper,  and  the  primordial  cell  the  ovum  with  its  ves- 
icle and  germinal  dot. 

PRACTICAL  DEMONSTRATION. 

The  ovary  from  a  still-born  babe  is  to  be~  removed  with  the 
scissors,  exercising  the  utmost  care  that  the  surface  be  not  touched. 
Place  immediately  in  strong  alcohol,  and  in  twenty-four  hours  it 
will  be  fit  for  cutting.  Cut  extremely  thin  sections  at  right  angles 
to  the  free  surface  and  including  the  same.  Stain  with  hsema.  and 
eosin.  Mount  in  dammar. 


OVARY   OF  HUMAN  FCETUS   OF  EIGHT   MONTHS. 

(Fig.  99.) 
OBSERVE: 

(L.) 

1.  The  free  surface.     (Note  the  occasional  depressions  which 
mark  the  involution  of  epithelia.) 

2.  The  layers.     (Note  the  absence  of  demonstrable  tunica 
albuginea  and  the  great  area  occupied  by  the  cortex.     The  vessels 
of  the  central  portions  are  unlike  the  ovary  of  mature  life;   large, 
not  numerous,  and  thin- walled.) 


148  PRACTICAL    MICROSCOPY. 

(H.) 
.  3.  The  primordial  ova  of  the  surface  epithelium. 

4.  The  projecting  lines  or  chains  of  epithelium  undivided. 
(Here  the  cells  seem  rather  elongate.) 

5.  Chains  which  are  in  process  of  subdivision. 

6.  Young  Graafian  follicles  in  columns  at  right  angles  to 
the  surface  of  the  ovary. 

7.  The  discus  proligerus,  in  many  instances  yet  composed  of 
flattened  cells. 


FIG.  99.— SECTION  OF  OVARY  OF  CHILD.    DEATH  TEN  DAYS  AFTER  BIRTH,    x  350. 

A.  Germinal  epithelium,  covering  surface  of  the  ovary. 

B.  Primitive  ova. 

C.  C.    Projection  of  surface  epithelium  within  the  organ. 

D.  Constriction  of  the  projected  chain  or  cord  of  epithelium  and  isolation  of  portions  to 
form  Graafian  follicles. 

E.  Chain  of  Graafian  follicles.    The  stroma  is  seen  filled  with  previously-formed  follicles 
which  have  become  now  isolated. 

F.  A  large  Graafian  follicle.    It  has  been  cut  in  half  ;  the  ovum  has  fallen  out ;  and  the 
membrana  granulosa  is  seen  lining  the  cup-shaped  cavity. 

G.  Large  arteries  of  the  central  portion  of  the  ovary. 

8.  Follicles  showing  discus  proligerus  as  columnar  cells. 

9.  Follicles  showing  great  proliferation  of  discus  pro- 
ligerus. 


DEVELOPMENT   OF  THE   OVUM.  149 

10.  Ova  in  early  development  from  primordial  cells,  with 
granular  vesicle. 

11.  Instances  of  development  of  two,  possibly  three,  ova 
in  a  single  follicle. 

12.  Large  blood-capillary  supply  of  cortex,  vessels  generally 
parallel  with,  the  Graafian  chains. 


150  PRACTICAL    MICROSCOPY. 


THE   SUPRARENAL  CAPSULE. 

These  bodies  are  attached  by  areolar  tissue  to  the  summit  of 
the  kidneys,  and  consist  of  several  folia  or  leaflets.  An  examina- 
tion of  one  of  these  leaves  will  give  us  an  idea  of  the  organ  as  a 
whole.  The  plan  of  structure  seems  to  be  as  follows: 

In  the  connective  tissue  which  supports  the  folia  are  found 
arterial  branches  derived  from  the  phrenic  (and  sometimes  from 
the  renal  before  it  enters  the  kidney).  These  arteries  penetrate 
the  organ,  break  up  immediately  into  capillaries,  which  finally  con- 
verge toward  the  centre  of  the  leaflet;  the  blood  is  here  collected 
in  thin-walled  veins,  by  which  it  is  drained  into  the  suprarenal 
vein,  thus  leaving  the  capsule. 

The  capillary  meshes  vary  in  form  and  size,  according  to  their 
position.  Near  the  circumference  of  the  leaves  the  meshes  are 
small  and  ovoid,  while,  as  the  centre  is  approached,  they  become 
elongated.  These  spaces  between  the  capillaries  are  filled  with 
compressed,  globular,  nucleated  cells,  the  smaller  containing  only 
perhaps  six  or  eight,  while  the  longer  may  be  occupied  by  thirty  or 
forty  of  these  cell  elements,  which  constitute  the  parenchyma  of 
the  organ.  This  variation  in  size  of  the  cell  compartments,  con- 
tributing, as  it  does,  to  alter  the  appearance  of  the  different  zones 
of  the  tissue,  has  given  rise  to  a  division  into  cortex  and  medulla, 
with  subdivisions  even  of  these.  There  is  no  histological  or  physi- 
ological difference,  as  we  believe,  between  the  different  parts  of  the 
folia  of  the  suprarenal  capsule,  except  as  has  been  indicated.  The 
structure  is  exceedingly  simple,  although  its  function  is  not  settled 
beyond  question. 


PRACTICAL  DEMONSTRATION. 

The  tissue  is  best  hardened  in  strong  alcohol,  and  should  be  cut 
as  soon  as  the  hardening  is  complete.  It  will  be  sufficiently  firm 
to  admit  of  the  thinnest  sections  being  made  free-hand  or  with  a 
simple  microtome.  The  cuts,  stained  with  haema.  and  eosin,  give 
excellent  differentiation. 


HUMAN    SUPRARENAL   CAPSULE.  151 

HUMAN   SUPRARENAL   CAPSULE.     (Figs.  100  and  101.) 

SECTION  OF  A  SINGLE  LEAFLET,  CUT  TRANSVERSELY  TO  THE  CEN- 
TRAL VEINS.  STAINED  WITH  H^EMA.  AND  EOSIN;  MOUNTED 
IN  DAMMAR. 

OBSERVE : 

(L.) 

1.  Section  of  arterial  twigs  on  the  border  of  the  leaflet. 

2.  The  convergence  of  the  parenchyma  toward  the  centre. 


FIG.  100.— VERTICAL  SECTION  OF  A  SINGLE  LEAFLET  OF  THE  STTPRAENAL  CAPSULE.    Stained 
with  Hsema.  and  Eosin.     X  60. 

A.  Fibrous  tissues  surrounding  and  connecting  the  leaflets. 

B.  The  outer  portion,  consisting  of  small  compartments — the  so-called  cortex. 

C.  The  central,  elongated  cell-compartments — medulla. 

D.  Large  thin-walled  central  veins. 

E.  Arteries  ramifying  in  the  outer  fibrous  tissue  which  supply  the  parenchyma. 

3.  The  large  and  thin-walled  central  veins. 

4.  The  small  size  of  the  parenchymatous  areas  on  the 
outer  borders  and  their  elongation  within. 


152 


PRACTICAL    MICROSCOPY. 


(H.)    Fig.  101. 

1.  The  capillary  plexus,  forming  ovate  or  elongate  meshes. 

2.  The  compressed  globular  cells  of  the  parenchyma.    (Note 
that  the  cells  are  small  in  the  small  compartments,  as  though 
crowded.     This  is  due,  in  a  measure,  to  the  contraction  of  the  tis- 
sue from  the  rapid  hardening.) 


FIG.  101.— SAME  SECTION  AS  FIG.  100,  MORE  HIGHLY  AMPLIFIED.    REGION  MIDWAY  BETWEEN 
THE  FIBROUS  INVESTMENT  AND  THE  CENTRE  OF  THE  LEAFLET,    x  400. 

A.  Blood-capillaries,  arising  from  the  arteries  seen  in  the  preceding  illustration ;  and  ram- 
ifying in  the  connective-tissue  framework. 

B.  Compartments — lobules — formed  by  delicate  connective-tissue  prolongations  from  the 
fibrous  capsule. 

C.  Lobular  parenchyma.    These  large  somewhat  rounded  cells  are  generally  mono- 
nucleated,  contain  fat>globules,  and  are  frequently  pigmented. 


3.  The  minute  fat-globules  in  the  parenchyma.     (This  I  be- 
lieve to  be  physiological,  and  not  unlike  the  fat-storing  observed  in 
the  parenchyma  of  the  liver.) 

4.  Yellow  pigment-granules  in  the  parenchyma. 


SALIVARY   GLANDS. 


153 


THE   SALIYAEY   GLANDS.     PANCKEAS. 
PLAN  OF   GLAND    STRTJCTTJBE. 

GLANDS. 

A  gland  is  an  organ — frequently  subsidiary  to  and  located  within 
other  organs — whose  cells  manufacture  from  the  blood  products  to 
be  utilized  in  the  maintenance  of  physiological  integrity. 

Glands  are  tubes  or  cavities,  with  connective-tissue  walls  lined 
with  cells  of  a  columnar  type.  Around,  and  in  close  proximity  to 
the  lining,  is  spread  a  plexus  of  blood  capillaries. 

The  essential  parts  of  a  gland  are,  therefore : 

1.  A  duct,  or  efferent  conduit  for  the  secretion. 

2.  Parenchyma,  cells  engaged  in  secretion. 

3.  A  blood- vascular  supply. 


TUBULAR   GLANDS. 

The  simplest  gland  structure  is  presented  in  the  form  of  a  tube. 
Glands  are,  frequently,  little  more  than  tubular  depressions  in 


FIG.  102.— DIAGRAM.    SIMPLE  TUBULAR  GLAND. 

A.  Lining  cells— parenchyma. 

B.  Capillary  plexus,  supplying  the  parenchyma. 

C.  Connective  tissue  supporting  capillaries. 

D.  Arterial  supply. 


154  PRACTICAL    MICROSCOPY. 

mucous  surfaces.     Examples  are  found  in  the  uterus,  stomach, 
small  intestine,  etc. 

COILED    TUBULAR   GLANDS. 

Tubular  glands  are  often  greatly  elongated,  with  the  blind  ex- 
tremity coiled.  This  variation  presents  the  simplest  differentia- 
tion between  the  part  of  the  tube  which  is  secretory,  and  the  duct, 
or  drainage  part.  With  this  change  in  function  of  the  different 
extremities  of  the  tube  will  occur  a  change  of  epithelium.  The 
cells  belonging  to  the  duct-end  will  usually  retain  the  columnar 
form;  while  the  actively  secreting  elements  will  become  enlarged, 


FIG.  103.— DIAGRAM.    COILED  TUBULAR  GLAND. 
Same  references  as  Fig.  102. 

more  nearly  filling  the  tube,  and  assume  a  polyhedral  form  from 
pressure. 

Examples  have  already  been  seen  in  the  sweat-tubes  of  the  skin 
— sudoriferous  glands — and  the  mucous  glands  of  the  submucosa 
of  the  larger  bronchi. 

BRANCHED  TUBULAR  GLANDS. 

With  the  branching  of  the  duct  portion  of  gland  tubules,  there 
usually  occurs  a  dilatation  of  the  extremities  into  alveoli,  although 
pure  examples  of  branched  tubular  glands  are  afforded  in  the  gas- 
tric and  intestinal  glands,  those  of  the  cervix  uteri,  etc. 

The  most  nearly  typical  branching  of  gland-like  tubules  is 
afforded  by  the  tubuli  uriniferi  of  the  kidney — although  not  con- 


ACINOUS   GLANDS. 


155 


tained  in  a  true  gland.     The  tubules  here  present  other  features 
peculiar  to  them,  which  will  be  referred  to  under  the  proper  head. 


FIG.  104.— DIAGRAM.    BRANCHED  TUBULAR  GLAND. 
References  same  as  Fig.  102. 


ACINOUS   GLANDS. 

The  dilatation  of  branching  tubules,  referred  to  under  the  pre- 
vious heading,  results  in  the  formation  of  acinous  glands.  They 
are  formed  by  the  subdivision  of  a  main  tube  or  duct,  with  repeated 
branching  of  the  secondary  tubules.  Collections  of  terminal 
branches  often  result  in  globular  masses  which  are  more  or  less 
perfectly  isolated  from  one  another  by  connective  tissue.  In  this 
way  compound  acini  are  produced,  such  as  the  pancreas,  the  sali- 
vary, mammary,  and  buccal  glands. 

The  acini  may  be  developed  into  alveoli — as  in  the  active  mam- 
mary, and  in  the  sebaceous  glands.  These  are  usually  filled  with 
polyhedral  cells,  or  with  the  products  of  fatty  degeneration  of  the 
same. 


156 


PRACTICAL    MICROSCOPY. 


FIG  105.— DIAGRAM.    ILLUSTRATING  THE  PLAN  OF  ACINOUS  GLANDS. 
References  same  as  Fig.  102. 


FIG.  106. — SECTION  OP  A  SMALL  PORTION  OP  THE  PAROTID  GLAND. 
Stained  with  Haema.  and  Eosin.     X  250. 

A.  Narrowing  of  the  duct  from  a  small  lobule,  before  entering  a  larger  duct. 

B.  Dilatation  of  a  duct  after  leaving  a  small  lobule. 

C.  Primary  lobules,  in  nearly  L.  S. 

D.  Acini  in  T.  S.,  showing  the  minute  lumen. 

E.  Connective  tissue  supporting  the  gland. 

F.  Striated  muscular  fibre  adjacent  to  the  gland. 

G.  Adipose  tissue  in  the  loose  areolar  tissue. 


THE    PAKOTID    GLAND. 


157 


THE   PAROTID    GLAND. 

The  Parotid,  Submaxillary,  SuUingual,  and  Buccal  Salivary 
Glands  are  typical  glandular  structures,  with  individual  peculiari- 
ties only  in  respect  to  the  cell  elements;  these  vary  according  to 
the  nature  of  the  secretion  formed  in  each. 

The  parotid  is  a  compound  acinous  gland,  leading  from  which 
is  a  principal  duct — lined  with  tall  columnar  cells — which  collects 
the  fluid  saliva  from  the  different  divisions  of  the  organ. 

As  the  duct  penetrates  the  gland  it  branches  freely/ the  lumina 
becoming  smaller  and  the  cells  shorter  as  the  deeper  parts  are  ap- 
proached. 

Each  terminal  duct  is  in  connection  with  several  acini.  The 
connective-tissue  adventitia  of  the  duct  becomes  the  thin  wall  of 


FIG.  107.— SECTION  OF  PART  OF  THE  SUBMAXILLARY  GLAND.    X  250. 

A.  Narrow  duct  from  terminal  lobules. 

B.  Small  duct  in  T.  S. 

C.  Small  duct  in  oblique  section. 

D.  Transversely-divided  acini,  showing  large  lumen. 

E.  Mucous  remaining  in  the  lumina. 

F.  Striated  muscular  fibres. 

G.  Adipose  tissue. 


158  PRACTICAL    MICKOSCOPY. 

the  acinus,  and  the  lining  cells  broaden,  frequently  become  poly- 
hedral, and  are  bluntly  pointed.     The  cells  so  nearly  fill  the  acini 
as  to  leave  a  small  and  not  easily  recognized  lumen. 
The  gland  is  richly  supplied  with  blood-vessels. 


THE   SUBMAXILLARY   GLAND. 

The  submaxillary  is  presented  as  an  example  of  a  typical  mucous 
gland.  As  I  have  previously  said,  the  general  arrangement  is  not 
unlike  that  of  the  other  salivary  glands. 

Similar  structures  are  found  in  the  submucosa  of  the  mouth, 
tongue,  fauces,  trachea,  and  the  larger  bronchi. 

Its  peculiarity  appears  in  the  parenchyma,  and  will  be  noticed 
later. 


FIG.  108.— SECTION  FROM  THE  PANCREAS. 

A.  Wall  of  a  large  duct. 

B.  The  somewhat  cubical  lining  cells. 

C.  Arteries. 

D.  Lumen  of  the  acini,  T  S. 

E.  Terminal  duct  entering  a  lobule. 

F.  Acini  in  L.  S. 


THE   PANCREAS.  159 


THE   PANCREAS. 

The  histology  of  the  pancreas  is,  in  general,  that  of  a  true  serous 
gland — e.g.,  the  parotid.  It  has  been  called  by  physiologists  the 
abdominal  salivary  gland. 

The  cells,  constituting  the  parenchyma,  are  somewhat  smaller; 
the  lobules  less  regular  in  size  and  form;  and  the  lumen  of  the 
acini  much  less  easy  of  demonstration,  in  an  ordinary  hardened 
section,  than  the  same  in  the  parotid.  The  vascular  supply  is  also 
more  abundant. 

The  branches  of  the  pancreatic  duct  are  provided  with  a  very 
thick  adventitia,  are  lined  with  short  columnar  cells,  and  seldom 
"present  the  dilatation,  which  generally  occurs  in  a  serous  gland,  on 
entering  the  lobule. 

PRACTICAL    DEMONSTRATION. 

PAROTID    AND    SUBMAXILLARY    GLANDS,   AND    THE    PANCREAS. 

The  tissue  must  be  fresh,  divided  in  small  pieces — not  larger 
than  a  quarter  of  an  inch  cube — and  hardened  by  placing  in  ninety- 
five  per  cent  alcohol  for  twelve  hours,  after  which  fresh  spirit 
should  be  substituted.  If,  after  the  lapse  of  another  twelve  hours, 
the  tissue  should  not  be  sufficiently  firm,  it  should  be  placed  in  a 
small  quantity  of  absolute  alcohol  for  three  hours.  Sections  should 
be  made  immediately  after  hardening — as  more  prolonged  action 
of  the  strong  spirit  will  cause  the  tissue  to  contract. 

Sections  may  be  cut  with  or  without  a  simple  microtome — the 
desideratum  being  thin  rather  than  large  cuts. 

Stain  lightly  with  hsema.  and  deeply  with  eosin. 

After  sections  of  hardened  tissue  have  been  examined,  the 
glandular  parenchyma  may  be  profitably  studied  in  teasings  from 
tissue  which  has  been  in  Miiller  twenty-four  hours.  Wash  the 
teasings  on  the  slide  with  a  liberal  supply  of  water,  removing  the 
same  from  time  to  time  with  blotting-paper.  Add  a  drop  of 
hsema.  solution;  and,  after  washing  this  away,  add  a  drop  of  gly- 
cerin, and  cover.  This  method  is  very  generally  useful  for  teased 
or  scraped  fragments  of  glandular  structures. 

.     (Figs.  106,  107,  and  108.) 
OBSERVE  : 

(L.) 

1.  The  connective  tissue.     (Most  abundant  in  the  parotid, 
and  least  so  in  pancreas.)' 

2.  The  ducts.     (Note  the  flattening  of  the  lining  columnar 
cells,  as  the  ducts  approach  the  acini,  until  mere  scales  result. 


160  PRACTICAL    MICROSCOPY. 

Also  the  thick  connective-tissue  adventitia,  especially  demonstrable- 
in  the  pancreas.) 

3.  The  lobules.     (These  are  formed  by  several  acini,  and  are 
typical  only  in  the  parotid — at  least  they  only  here  appear  well 
formed.     It  must  be  remembered  that  only  one  plane  is  visible, 
and  that  there  is  little  perspective.) 

4.  The  acini.      (Note  the  lumina — large  in  the  submaxil- 
lary,  less  so  in  the  parotid,  and  least,  and  often  difficult  to 
make  out,  in  the  pancreas. 

5.  The  blood-vessels,  muscular  and  adipose  tissue.     (The 
two  latter  are  demonstrable  only  in  the  salivary  glands,  and  do  not 
belong  properly  to  the  gland  itself.     The  capsule  of  the  pancreas, 
in  common  with  such  structures  in  general,  contains  adipose.     The 
abundant  inter-acinous  capillary  plexuses  of  the  pancreas  require 
the  high  power  for  satisfactory  demonstration.) 

(H.) 

6.  The  parenchyma,     (a)  The  small  but  distinct  shortened 
columnar  cells  of  the  acini  of  the  parotid.     (Observe  that  they 
are  frequently  so  formed  that  the  convexity  of  one  cell  fits  into 
the  concavity  of  its  neighbor.     Where  seen  in  transverse  section, 
the  outline   is  a  polygon.      Note  especially  the  change   in  the 
parenchymatous  elements  as  the  terminal  duct  merges  into  an 
acinus.) 

(b)  The  large,  swollen  cells  of  the  mucous  gland — sub- 
maxillary.     (Observe   the  comparatively  clearness   of  the  cells. 
They  contain  a  very  delicate  reticulum,  and  their  nuclei  are  often 
obscured  and  frequently  seen  to  be  placed  at  the  junction  of 
the  cells.) 

(c)  The  rounded,  often  polyhedral  cells  of  the  pancreas. 
(They  resemble  the  parotid  elements,  although  smaller  and  less 
granular.) 


THE   LYMPHATIC    SYSTEM.  161 


THE  LYMPHATIC   SYSTEM. 

The  Lymphatic  System  is  a  circulatory  apparatus  of  exceedingly 
complicated  arrangement.  It  comprises : 

1.  A  system  of  irregular  clefts  and  cavities  which  are  of  almost 
universal  distribution  in  the  more  solid  tissues,  in  the  framework 
and  parenchyma  of  organs,  around  blood-vessels  and  viscera. 

2.  Nodules  of  sponge-like  tissue,  improperly  called  lymphatic 
glands. 

3.  Channels   of  communication,   consisting  of  capillaries  and. 
ducts. 

4.  A  central  reservoir — the  receptaculum  chyli. 

5.  Large  efferent  ducts,  by  means  of  which  the  contents  of  the 
system  are,  eventually,  poured  into  the  blood,  in  both  sides  of  the 
neck  at  the  junction  of  the  internal  jugular  and  subclavian  vein. 

6.  A  fluid,  lymph,  containing    numerous  nucleated   bodies  or 
lymphoid  cells,  and  various  substances  in  solution. 

The  whole  provides  a  channel  for  the  introduction  of  formed 
and  nutrient  elements  into  the  blood;  as  well  as  affording  drain- 
age for  the  tissues,  the  products  of  which  are  also  emptied  into  the 
blood-vascular  system,  to  be  afterward  eliminated  by  special  organs. 

The  circulating  lymph  always  passes  in  a  direction  toward  the 
venous  system.  This  current  is  established  in  some  of  the  lower 
animals  by  means  of  distinct,  pulsating,  hollow  organs,  or  lymph 
hearts;  but  no  corresponding  structure  exists  in  man,  and  the  sys- 
tem becomes  here  subordinated  to  the  blood-vascular  apparatus. 

In  man,  the  maintenance  of  the  lymph-flow  is  due  largely  to  a 
negative  pressure,  consequent  upon  the  connection  between  the 
termini  of  the  lymph-vessels  and  the  veins.  Without  doubt  the 
pumping  motion  of  the  intestinal  villi  presents  a  factor  in  the  es- 
tablishment of  a  current  in  the  lacteals  toward  the  mesenteric  ves- 
sels. The  perivascular  lymph  receives  an  impetus  with  each  cardiac 
systole.  The  muscular  contractions  of  inspiration  contribute  motil- 
ity  to  the  contents  of  the  diaphragmatic  lymph-channels,  in  a 
direction  against  gravity.  Indeed,  the  contractions  of  nearly  every 
muscular  fibre,  whether  skeletal  or  organic,  lend  their  aid  to  lymph, 
propulsion. 

The  direction  of  the  lymph-current  is  determined  by  valves; 
which  resemble,  somewhat,  those  of  the  veins. 

Cavities  lined  with  so-called  serous  membranes,  may  be  consid- 
ered as  expanded  lymph- channels. 
11 


162 


PRACTICAL    MICROSCOPY. 


LYMPH  CHANNELS. 

The  larger  and  more  regularly  formed  channels  for  lymph  cir- 
culation, such  as  the  mesenteric  and  thoracic  ducts,  do  not  differ, 
materially,  in  structure,  from  correspondingly  sized  veins.  The 
irregular  clefts  in  the  interstices  of  fibrous  tissues,  serving  as  the 
primitive  lymph-containing  channels,  have  been  already,  and  re- 
peatedly, noticed.  Fig.  109,  although  purely  diagrammatic,  will 
serve  to  show  the  relation  of  this  system  to  the  blood-vessels.  A 
perivascular  lymphatic  channel  is  a  sort  of  tubular  investment  of 


JNTIMA 
MEDIA 
ADVENTITIA 
(PEfWASCULAR 

I    SPACE 


FIG.  109.— DIAGRAM.    ARTERY  IN  TRANSVERSE  SECTION,  SHOWING  THE  PERrvAsctriAR 

LYMPH-SPACE. 


the  blood-vessel,  lined  with  flattened  endothelia  sending  prolonga- 
tions inward;  these  prolongations  branch,  and  are  finally  in  com- 
munication with  a  layer  of  cells  covering  the  adventitia.  In  this 
manner,  in  close  apposition  to  parts  of  the  vascular  system,  a  sys- 
tem of  channels  is  provided,  within  which  the  lymph  may  slowly 
percolate. 

The  largest  lymphatic  channels  in  the  human  body  are  the  cav- 
ities of  the  peritoneum  and  pleurae.  They  are  in  connection  one 
with  the  other,  and  with  the  lymphatic  system  generally;  and 
these  channels  of  communication  between  the  great  abdominal  and 
thoracic  lymphatic  cavities  present,  perhaps,  as  the  most  convenient 
and  typical  for  demonstration. 


LYMPH   CHANNELS.  163 

PRACTICAL   DEMONSTRATION. 

LYMPHATIC    VESSELS    OF   THE    CENTRAL   TENDON    OF   THE    DIA- 
PHRAGM. 

(Figs.  110  and  111.) 

This  demonstration  had  best  be  made  with  tissue  from  the  rab- 
bit, inasmuch  as  the  slightest  decomposition  of  the  epithelium 
would  be  fatal  to  success. 

A  small  (preferably  white)  rabbit  should  be  quickly  killed  by 
decapitation,  and  immediately  suspended  by  the  hind  legs,  so  as  to 
thoroughly  drain  the  body  of  blood.  As 'soon  as  the  blood  has 
ceased  dripping,  open  the  thoracic  cavity  by  slitting  up  the  skin 
along  the  median  line,  pushing  it  to  the  sides  and  removing  the 
sternum.  In  this  operation,  work  rapidly  and  avoid  soiling  the 
internal  parts.  Then  with  the  fingers  of  one  hand  raise  the  lungs 
and  heart  from  the  diaphragm,  and  with  a  large  camel's-hair  brush 
proceed  to  quickly,  and  quite  forcibly,  pencil  the  white  glistening 
surface  of  the  central  diaphragmatic  tendon,  moistening  the  brush 
from  time  to  time  in  the  lymph  of  the  pleural  cavity.  Should  the 
quantity  of  fluid  be  small,  add  a  little  distilled  or  previously-boiled 
and  filtered  water.  The  object  of  the  brushing  is  -to  remove  the 
epithelial  cells  which  cover  the  surface,  and  which  would  otherwise 
hide  the  lymph-spaces.  After  the  pencilling,  drain  away  the  fluid, 
and  pour  over  the  brushed  surface  a  solution  of  one  grain  of 
nitrate  of  silver  to  an  ounce  of  distilled  water.*  Allow  the  silver 
solution  to  remain  for  twenty  minutes  in  contact  with  the  tissue, 
the  body  meanwhile  being  kept  away  from  the  bright  sunlight; 
then  pour  off  the  solution,  wash  the  surface  twice  with  distilled 
water,  and  afterward  allow  water  from  the  tap  to  flow  over  the 
parts  for  at  least  five  minutes. 

If  you  observe  the  directions  carefully,  the  surface  of  the 
tendon  will  lose  its  original  glistening  appearance  and  become 
whitish  and  opaque. 

The  tendon,  or  such  portion  of  it  as  you  wish  to  preserve,  may 
be  cut  out  with  the  scissors  after  the  washing,  thrown  into  gly- 
cerin, and  placed  in  the  sunlight  until  the  surface  becomes  brown. 
With  the  forceps  tear  off  small  pieces  of  the  stained  side,  say  one- 
half  inch  square,  and  examine  in  glycerin,  or  mount  them  perma- 
nently in  the  same  medium. 

The  demonstration  of  the  channels  of  the  lymphatic  system  is 
based  upon  the  following: 

1.  Lymph-channels  are  always,  however  small  or  irregular,  lined 
with  flattened  cells  in  a  single  layer — i.e.,  pavement  endothelium. 

2.  The  lining  cells  are  cemented  together  with  an  albuminous 
substance. 

*  Water  which  has  been  well  boiled  in  a  clean  vessel,  and  afterward 
carefully  filtered,  may  be  generally  employed  in  histological  work  when 
distilled  water  is  not  available. 


164  PRACTICAL    MICROSCOPY. 

3.  Nitrate  of  silver  combines  with  the  cement,  forming  albumi- 
nate  of  silver,  which  becomes  dark  brown  when  exposed  to  light. 

If  you  have  been  successful,  the  silver  will  have  penetrated  the 
tendon,  and  mapped  out  the  lymph-channels,  indicating  an  outline 
of  every  lining  cell  by  means  of  a  dark  border.  Failure  will  result 
only  from  non-attention  to  cleanliness  in  the  handling  of  the  tis- 
sue; the  silver  in  which  case  becomes  deposited  generally  over  the 
surface.  The  margins  or  outlines  of  the  cells,  it  must  be  remem- 
bered, are  stained  with  the  silver.  The  nuclei  may  be  demon- 
strated by  after-staining  with  dilute  hgema.,  or  better,  borax- carmine. 
The  mounting  may  be  done  in  dammar,  although  the  elastic  fibres, 
of  .which  the  matrix  of  the  tendon  is  composed,  will  become  stiff 
during  immersion,  and  show  a  tendency  to  curl  and  contract.  If 
glycerin  be  used  after  carmine-staining,  tissues  should  be  washed 
thoroughly  in  water,  subsequently  to  the  oxalic-acid  bath,  trans- 
ferred to  equal  parts  of  glycerin  and  water,  and  allowed  to  remain 
for  an  hour,  at  least,  before  mounting. 


CENTRAL   TENDON   OF   THE   DIAPHRAGM.     SILVER- 
STAINING.    (Vide  Figs.  110,  111.) 
OBSERVE  : 
(L.) 

1.  The  division  of  the  specimen  into  dark  and  light  areas. 
(The  dark  areas  represent  the  more  solid  portions  of  the  tissue  or 
the  partitions  between  the  channels,  and  the  light  spaces  are  the 
lymph  paths.) 

2.  The  lymph  paths — the  light  spaces.     (These  show,  with 
this  amplification,  as  irregular,  winding,  and  anastomosing  courses, 
marked  with  very  delicate  lace-like  tracery — the  silver  lines.) 

3.  Valves  of  the  lymph  paths.     (At  points,  the  paths  will  be 
crossed  by  dark  curved  lines.     These  are  imperfect  valves,  not  un- 
like a  single  cusp  of  an  aortic  valve.) 

(H.) 

4.  Outlines  of  the  cells  lining  the  larger  excavations 

(lymph  paths)  in  the  tissue.  (Note  that  the  cells  are  generally 
elongate  in  the  direction  of  the  lymph  path.  The  edges  are  fre- 
quently serrated.) 

5.  Stomata,  minute  openings  at  the  junction  of  several  cells. 

6.  The  construction  of  the  valves.    (These  are  curved  against 
the  lymph  flow,  and  covered  with  cells  like  other  parts  of  the 


CENTRAL    TENDON    OF    THE   DIAPHRAGM, 


165 


channel.     Note  the  change  in  form  of  the  cells  approaching  and 
covering  the  valves.) 

7.  Elastic  fibres  of  the  more  solid  parts  of  the  tendon. 

8.  Lymph  capillaries.     These  will  be  seen  in  the  partitions 
between  the  larger  paths.     In  places  they  may  be  observed  empty- 
ing into  the  paths,  and  again  will  appear  as  simple  cavities,  accord- 
ing to  the  manner  sectioned.) 

9.  The  deeper  capillaries.     (Careful  focussing  the  portions 


FIG.  110.— LYMPH-CHANNELS.    CENTRAL  TENDON  OF  DIAPHRAGM  OF  RABBIT.    SILVER 
STAINING,     x  60. 

The  dark  portions  represent  the  more  solid  portions  of  the  tissue. 

The  light  areas  are  the  lymph-channels;  and  the  direction  of  the  flow  is  shown  by  the 
arrows. 

The  minute  lines  in  the  lymph-spaces  are  the  silver-stained  cement  boundaries  of  the 
pavement  cells  lining  the  channels. 

The  valves  appear  as  curved  lines  in  the  lymph-spaces. 


of  the  tendon  which  appear  most  solid  will  reveal  minute  cell-lined 
channels  or  capillaries.  The  student  must  remember  that  we  can- 
not penetrate  tissues  with  the  microscope  to  any  considerable  depth, 
but  are  restricted  to  nearly  a  single  plane.  If  it  were  possible  to 


166  PRACTICAL    MICEOSCOPY. 

penetrate  with  the  eye  the  entire  thickness  of  the  tendon,  we  might 
trace  the  lymph  paths  or  channels  from  the  abdominal  to  the 
thoracic  surface.) 


FIG.  111.— A  SMALL  PORTION  OP  SPECIMEN  SHOWN  IN  FIG.  110,  MORE  HIGHLY  MAGNIFIED. 

X350. 

A,  A,  A.    Large  lymph-channel. 

B.  Valve  in  the  course  of  last. 

C,  C,  C.    Lymph-capillaries  in  the  more  solid  parts  of  the  tendon. 

D.  Pavement  cells  upon  which  a  large  amount  of  silver  has  deposited.    Failure  to  follow 
the  instructions  for  the  staining  frequently  results  in  a  like  deposition  of  silver  over  the 
whole  surface. 


LYMPHATIC    NODES    OR   GLANDS.  167 


LYMPHATIC  NODES  on  GLANDS. 

At  numerous  points  along  the  course  of  lymphatic  vessels  they 
penetrate  small  nodules  of  so-called  adenoid  tissue,  which  have 
been  termed  lymphatic  glands.  They  are  frequently  microscopic; 
others,  again,  not  unusually  attain  the  size  of  a  large  pea.  They 
secrete  nothing,  hence  are  not  glands.  They  are  somewhat  sponge- 
like  in  structure,  and  the  lymph  filters  slowly  through  them. 

Most  frequently  several  ducts  enter  one  of  these  larger  nodes, 
while  perhaps  only  a  single  efferent  will  be  found. 

The  histology  of  a  lymph  node  is  not  always  easily  compre- 
hended by  the  student,  and  I  have  endeavored  to  make  a  diagram 
(Fig.  112)  that  would  simplify  the  matter  somewhat.  They  are  en- 
veloped by  a  capsule  of  connective  and  involuntary  muscular  tis- 
sue, which  sends  trabeculce,  into  the  body  of  the  organ,  and  these 
branching  posts  support  the  structure  as  a  framework.  The  inter- 
stices are  quite  small  in  the  more  central  portion  and  larger  toward 
the  periphery;  this  has  resulted  in  the  application  of  the  terms 
medullary  and  cortical  to  the  respective  parts.  The  nutrient 
blood-vessels  are  contained  in  the  framework.  The  compartments 
contain  the  structure  peculiar  to  the  lymphatic  system — viz.,  ade- 
noid tissue. 

Adenoid  tissue  consists  of  a  mass  of  flattened  cells,  with  numer- 
ous delicate  fibrillar  prolongations,  which  branch  and  anastomose 
so  as  to  form  an  interwoven  structure — the  adenoid  reticulum. 
Klein  regards  the  cells  as  forming  no  essential  part  of  the  struc- 
ture, but  considers  them  as  flattened  plates  attached  to  the  fibrils.. 
The  meshes  of  the  adenoid  reticulum  are  in  connection  with  the 
fibres  of  the  trabeculae  and,  with  exception  of  the  portion  next  the 
latter,  are  filled — crowded,  in  fact — with  countless  small  spherical 
lymphoid  cells.  Those  portions  of  the  tissue  which  contain  the 
cells  are  termed  follicular  cords. 

The  lymph  path  is  the  portion  between  the  fibrous  trabeculae 
and  the  follicular  cords. 

When  we  learn  that  the  trabeculae,  follicular  cords,  and  lymph 
paths  each  pursue  very  tortuous  and  branching  routes,  we  can  ap- 
preciate the  complexity  of  the  organ  as  a  whole. 

The  blood-vessel  arrangement  presents  no  anomalies.  The 
small  arterial  trunks  enter  within  the  trabeculas,  finally  break  into 
capillaries  which  supply  the  follicular  cords,  etc.,  and  the  blood  is 
then  collected  by  the  venules  for  the  efferent  veins. 


168 


PRACTICAL    MICROSCOPY. 


Small  diffuse  collections  of  adenoid  tissue  have  already  been 
seen  in  many  organs.  These  do  not  differ  essentially  from  the 
tissue  just  described,  excepting  that  there  is  no  definite  arrange- 
ment of  trabeculae  and  lymph  paths,  as  in  the  compound  lymph 
node;  the  lymph  simply  filters  through  the  reticulum,  the  same 
being  a  part  of  the  lymph-channel  system  of  the  tissue  in  which 
the  adenoid  structure  may  occur. 


FIG.  112.— DIAGRAM.    PERIPHERAL  PORTION  OF  A  LYMPH-NODE. 

A,  A.    Afferent  lymph- vessels. 

B.  Capsule  of  the  node,  with  lymph-spaces  C.  C. 

D,  Trabecula  of  connective  tissue. 

E,  E,  E.    Lymph  path  in  the  node. 

F,  F.    Follicular  cords. 

G,  G,  G.    Lymphoid  cells  in  the  cell  network  of  the  paths. 
H,  H.    Blood-capillaries  of  the  cords. 

The  arrows  show  course  of  lymph. 


SECTION    OF    MESENTEKIC    LYMPHATIC    NODE.  169 


PEACTICAL   DEMONSTRATION. 

The  mesenteric  lymphatic  nodes  present  the  most  typical  struc- 
ture, and  may  be  obtained  from  the  human  subject,  if  fresh,  al- 
though those  from  the  dog  are  preferable,  on  account  of  the  better 
condition  of  the  tissue  as  usually  secured. 

The  nodes  should  be  sliced  in  half,  placed  in  Miiller  for  a  week, 
and  then  hardened  l^y  two  days'  immersion  in  strong  alcohol. 

Sections  should  be  mounted,  of  two  kinds,  viz.,  those  including 
the  whole  area  of  the  node — which  need  not  be  very  thin — for  dem- 
onstration of  the  scheme  or  plan  of  structure,  and  exceedingly 
thin  ones,  even  though  they  may  include  only  a  small  part  of  the 
organ,  for  study  of  the  details  of  the  adenoid  reticulum.  The  lat- 
ter purpose  will  be  subserved  by  shaking  a  number  of  thin  cuts  in 
a  test-tube  with  alcohol  for  a  few  minutes,  and  with  considerable 
violence,  even  to  the  sacrificing  of  most  of  the  sections.  The  agi- 
tation will  dislodge  the  lymph  cells,  which  otherwise  would  obscure 
the  histology  of  the  follicular  cords. 

Stain  deeply,  with  hsema.  and  eosin,  and  mount  the  thicker 
sections  in  dammar,  and  those  especially  thin  in  glycerin. 


SECTION   OF   MESENTEKIC   LYMPHATIC   NODE. 

(Figs.  113  and  114.) 
OBSERVE: 
(L.) 

1.  The   fibrous   capsule.     (Note   the   elongate   dots   in  the 
deeper  parts  of  the  capsule — the  nuclei  of  the  smooth  muscular 
tissue,  the  thick-walled  arteries,  the  lymph  spaces.) 

2.  The  trabeculae.     (Trace  these  as  they  penetrate  the  organ 
and  observe  that  they  frequently  end  abruptly,  on  account  of  hav- 
ing curved,  so  as  to  leave  the  plane  occupied  by  the  section.     The 
trabeculae  are  not  partitions,  like  the  interlobular  pulmonary 
septa  or  the  prolongations  from  the  capsule  of  Glisson  in  the  liver; 
they  are  not  unlike  rods  or  posts,  making  a  framework  and  not 
producing  alveoli.     Find  one  divided  transversely.) 

3.  The  follicular  cords.     (They  are  recognized  as  granular 
masses  between  the  trabeculaa.    Observe  the  varying  forms,  largest 
and  more  spherical  or  ellipsodial,  near  the  periphery — cortex. 
The  smaller  ones  of  the  central  region  (medulla)  must  not  be 
overlooked,  as  the  differentiation  is  sufficiently  marked  between 
them  and  the  variously  sectioned  trabecula3.) 

4.  The  lymph  p-aths.     (These  can  be  appreciated  by  remem- 


170 


PRACTICAL    MICROSCOPY. 


bering  that  the  follicular  cords  do  not  entirely  fill  the  spaces  be- 
tween the  trabeculae,  and  that  the  area  between  the  two — i.e.,  outside 
the  cords — is  the  more  open  in  texture,  and  contains  the  filtering 
lymph.  They  are  more  distinct  in  the  cortex.) 


FIG.  113.— VERTICAL  SECTION  OF  A  LYMPH-NODE  FROM  THE  MESENTERY,    x  66. 

A.  Capsule  of  node. 

B.  Lymph-spaces  in  the  last. 

C.  C.    Trabeculae,  L.  S. 

D.  D.    Follicular  cords,  L.  S. 

E.  Obliquely  sectioned  trabecula. 

F.  F.    Large  blood-vessels  of  the  central  portion  of  the  node. 

G.  Trabecula  in  T.  S. 

H.    Follicular  cord  in  T.  S. 

I.    Small  and  irregular  cords  of  the  centre  of  the  node. 

J.    Obliquely  sectioned  trabecula  of  the  centre  of  the  node. 

K,  K,  K.    Lymph-paths. 


(H.) 

5..  The  histology  of  the  capsule,  (a)  The  closely-united 
connective  tissue  with  the  scattering  elastic  fibres  of  the  external 
layer,  (b)  The  smooth  muscle  of  the  deeper  portions,  (c) 
Sections  of  arteries.  (These  may  present  of  considerable  size.) 
(d)  The  lymph  spaces.  (The  differentiation  is  by  the  flattened 
endothelia  of  spaces  which  otherwise  would  be  supposed  mere 
rifts  in  the  tissue,  inasmuch  as  no  definite  or  special  wall  can  bo 
detected.) 

6.  The  structural  elements  of  the  trabeculae.  (They  are 
similar  to  those  of  the  capsule,  excepting  the  elastic  element,  which 


SECTION   OF   MESENTERIC   LYMPHATIC    NODE.  171 

cannot  here  be  demonstrated.     Note  the  variously  sectioned  small 
arteries.) 

7.  The  follicular  cords.  (In  the  thicker  section,  the  field 
will  be  completely  crowded  with  lymphoid  cells.  Select  a  thin 
field  and  observe:  (a)  The  lymphoid  cells.  (These  will  be  found 
varying  in  size  from  a  very  small  red  blood-disc  to  that  of  a  large 
white  corpuscle;  some  are  filled  with  granules  only,  and  others 
with  one,  two,  and  even  three  nuclei.)  (b)  The  branching  endo- 
thelioid  cells,  (c)  The  delicate  fibrillae  of  the  adenoid  reticu- 


FIG.  114.— FRAGMENT  OF  SECTION  SHOWN  IN  FIG.  113.    MORE  HIGHLY  MAGNIFIED.    X  350. 

A.  Trabecula. 

B.  Follicular  cord. 

C.  Lymph-path. 

D.  Large  branching  cells  of  the  path  network.     . 

E.  Capillaries  of  the  cord. 

lum.  (You  may  endeavor  to  determine  whether  this  reticulum 
exists  as  an  offshoot  of  the  endothelioid  cells,  or  whether  the  latter 
are  simply  adherent  to  the  broadened  plates  of  the  former.) 

8.  The  reticulum  of  the  lymph  paths.     (Observe  that  this  is 
precisely  like  the  reticulum  of  the  follicular  cords,  as  demonstrable 


172  PRACTICAL    MICROSCOPY. 

after  shaking  out  most  of  the  lymph  corpuscles  of  the  last.)  (a) 
The  connection  between  the  fibrillae  of  the  paths  and  those 
of  the  trabeculae. 

9.  Capillaries  of  the  paths  and  cords.  (These  will  be  recog- 
nizable only  by  the  regular  succession  of  the  contained  red  blood- 
corpuscles.) 


THE    SPLEEN. 


ITS, 


THE  SPLEEK 

The  spleen  presents  no  regular  subdivision  of  parts  which  may 
bfe  studied  separately  and  combined  afterward,  as  we  are  able  to  do 
wiT'h  organs  like  the  lung,  liver,  etc.  The  spleen  is  a  ductless  organ 
or  so-called  gland,  and  the  plan  or  scheme  may,  perhaps,  be  best 
comprehended  by  following  the  blood  distribution. 

The  splenic  artery  enters  the  organ,  supported  by  a  considera- 
ble amount  of  connective  tissue,  and  rapidly  breaks  into  smaller 
branches,  from  which  the  arterioles  leave  at  right  angles.  The  arte- 
rioles  quickly  merge  into  capillaries,  which  form  plexuses  through- 


FIG.  115.— DIAGRAM.    SHOWING  THE  COURSE  OF  BLOOD  IN  THE  SPLEEN. 

out  the  different  portions  of  the  organ.  Here  we  meet  with  an 
anomalous  structure. 

The  capillaries,  instead  of  uniting  to  form  venules  as  in  the 
usual  vascular  plan,  empty  their  contents  into  small  chambers  or 
sponge-like  cavities — the  venous  spaces.  The  blood,  after  filtering 
through  these  venous  interstices,  is  collected  in  larger,  irregular, 
vein-like  channels,  which  finally  conduct  the  blood  into  the  veins 
proper  and  out  of  the  spleen. 

The  tissue,  containing  the  vascular  arrangement  described  in 
the  last  paragraph,  is  called  spleen  pulp. 

The  fibrous  capsule  which  envelops  the  spleen  sends  trabeculae 


174  PRACTICAL    MICROSCOPY. 

within,  which  form  a  framework;  and  from  this  fibrils  are  sent  off 
which  branch,  broaden,  and  inosculate  to  form  the  venous  chambers 
of  the  pulp. 

The  arteries  are  frequently  surrounded  by  nodules  of  adenoid 
tissue,  sometimes  globular,  more  frequently  considerably  elongated, 
and  following  the  vessel  for  a  considerable  distance.  These  nodules 
are  called  Malpigliian  bodies.  They  bear  no  resemblance  to  simi- 
larly named  structures  in  the  kidney,  excepting,  perhaps,  when 
seen  in  transverse  section  by  the  naked  eye. 

The  spleen  will  thus  be  seen  to  consist  of  a  fibrous  trabeculated 
framework,  the  pulp,  blood-vessels,  and  more  or  less  isolated  nodules 
of  adenoid  tissue. 


PRACTICAL  DEMONSTRATION. 

The  organ  must  be  absolutely  free  from  decomposition.  If 
human  tissue  cannot  be  obtained  in  good  condition,  recourse  may 
be  had  to  the  ox,  which  will  provide  an  excellent  substitute.  The 
small  supernumerary  spleens,  not  infrequently  found  during  post- 
mortem work,  are  most  desirable,  as  sections  can  be  easily  made 
through  the  entire  organ. 

Pieces  of  tissue  half  an  inch  cube,  including  a  portion  of  the 
capsule,  should  be  hardened  as  directed  for  lymph  nodes.  Sections 
are  easily  made  without  the  microtome,  as  the  mass  is  very  firm ; 
they  should  be  thin  and  stained  with  borax-carmine,  and  mounted 
in  dammar  or  in  glycerin. 


SECTION  OF  HUMAN  SPLEEN,  CUT  AT  RIGHT  ANGLES 
TO   AND   INCLUDING  THE   CAPSULE.     (Fig.  116.) 

OBSERVE:  , 

(i.) 

1.  The  fibrous  capsule,     (a)  Its  division  into  two  very  dis- 
tinct portions  or  layers,     (b)  The  clear  translucent  appearance 
of  the  tissue  (elastic)  of»the  outer  layer,     (c)  The  darker  deep 
layer  with  elongate  nuclei.     (The  elastic  element  of  the  capsule 
not  infrequently  becomes,  in  the  human  subject,  considerably  in- 
creased; and  this  development  occurs  irregularly,  sometimes  in  the 
form  of  minute  nodules.     I  do  not  know  that  they  present  any 
pathological  significance.) 

2.  The  trabeculae.     (The  depth  to  which  they  may  be  traced 
will  depend  largely  upon  the  direction  of  the  section.)     (a)  That 
these  are  not  bands,  but  bundles,  more  or  less  circular,  in  trans- 


SECTION    OF   HUMAN    SPLEEN. 


175 


yerse  section,  (b)  Their  irregular  course,  quickly  after  leaving 
the  surface,  (c)  That  occasionally  a  small  artery  may  be  found 
within  them,  though  they  are  usually  destitute  of  large  vessels. 
(d)  The  elongate  nuclei  of  the  muscular  fibre  largely  forming 
the  trabeculae. 

3.  The  large  blood-vessels,     (a)  The  arteries  more  frequent 


FIG.  116.— SECTION  OF  THE  SPLEEN,    x  60. 

A.  Elastic  portion  of  the  capsule. 

B.  Lymph-spaces  of  last. 

C.  Involuntary  muscular  portion  of  capsule. 

D.  Deeply  pigmented  portions  of  capsule. 

E.  E.    Trabeculae  from  C. 

F.  Trabeculae  in  oblique  section. 

G.  G.    The  spleen  pulp. 

H,  H.    Large  arteries  in  T.  S. 

I.    Arteries  in  L.  S. 

J.    Adenoid  nodule,  not  connected  with  an  artery. 

K.    Adenoid  nodule. — Malpighian  body — along  course  of  artery. 

L.    Adenoid  nodule  in  T.  S. 

M.    Vein. 

than  veins,     (b)  Their   very  prominent   adventitia.     (c)  Their 
tortuous  course. 

4.  The  adenoid  tissue.     (This  you  will  be  enabled  to  recog- 
nize by  the  great  number  of  lymphoid  cells  of  the  adenoid  struc- 


176  PRACTICAL    MICROSCOPY. 

ture,  the  nuclei  of  which  become  stained  very  deeply  blue  with 
haema.,  giving  a  very  distinct  differentiation.  At  this  point,  ex- 
amine every  part  of  the  specimen,  and  endeavor  to  detect  even  the 
most  minute  collection  of  this  tissue.)  (a)  Around  arteries,  con- 
stituting the  so-called  Malpighian  bodies,  (b)  Transverse 
sections  of  Malpighian  bodies,  noting  that  the  vessel  is  sel- 
dom in  the  centre  of  the  nodule,  (c)  Nearly  longitudinal 
sections  of  Malpighian  nodules,  observing  that  the  adenoid  tis- 
sue usually  follows  or  surrounds  the  artery  for  a  short  distance 
only,  (d)  That  the  distribution  is  not  confined  to  the  arteries,  but 
is  quite  common  around  trabeculae  and  beneath  the  capsule. 

5.  The  Spleen-pulp.     (This  will  be  found  in  those  portions  of 
the  section  not  occupied  by  structures  previously  demonstrated; 
and  will  be  determined  by  its  light  color.     Review  the  whole  arear 
and  endeavor  to  differentiate  every  portion  of  the  adenoid  and  pulp 
tissue.     The  staining  will  have  been  your  principal  guide  thus  far, 
the  pulp  elements  appearing  in  strong  contrast  by  their  pink  eosin 
color.) 

(H.) 

6.  The  structural  elements  of  the  capsule,     (a)  The  nu- 
merous minute  lymph-spaces  and  the  imperfect  vascular 
supply,     (b)  The  nuclei  of  the  peritoneal  cell  covering.    (This 
presupposes  that  the  section  has  been  selected  so  as  to  include  the 
peritoneal   investment.)      (c)    The   abundant   and   closely-packed 
elastic  fibrillae.     (d)  The  muscle  nuclei  of  the  deeper  parts,     (e) 
Cells  containing  granular  yellow  pigment.     (The  quantity  varies 
largely  with  different  specimens.) 

7.  The  Malpighian  nodules,    (a)  The  arterioles— very  small 
and  apt  to  escape  attention  unless  filled  with  blood-corpuscles.     (b) 
The  adenoid  reticulum.     (This  will  be  difficult  of  satisfactory 
demonstration,  excepting  the  section  be  thin.) 

8.  The  elements  of  the  pulp,     (a)  Large  flattened  cells, 
the  branches  forming  the  meshwork  of  venous  channels.     (These 
are  only  susceptible  of  very  satisfactory  demonstration  in  the  spleen 
of   leucocytlicemia.)     (b)  Red   blood-corpuscles.     Very  numer- 
ous and  often  broken  and  distorted,     (c)  Blood  pigment,     (d) 
Lymphoid  or  white  blood-corpuscles. 


SECTION   OF   THE  TIIYMU8   BODY..  177 


THYMUS    BODY. 

The  thymus  body  (frequently  and  improperly  called  a  gland)  is 
an  adjunct  to  the  lymphatic  system  of — in  man — foetal  and  infan- 
tile life;  disappearing,  by  an  atrophic  process,  at  or  before  the  age 
of  puberty. 

It  is  enveloped  by  a  fibrous  capsule,  partitions  from  which  sub- 
divide the  organ  into  lobes  and  lobules.  The  lobules  are  generally 
subdivided  into  follicles,  which  are  irregularly  sized  and  shaped, 
while  tending  to  an  ovoid  form. 

It  is  in  connection  with  the  general  lymphatic  system  by  pe- 
ripheral, afferent  lymph-channels;  and  by  efferent  vessels  which 
emerge  from  the  hili  of  the  lobes — the  lymph  having  meanwhile 
traversed  the  mesh-like  structure  of  adenoid  tissue  composing  the 
follicles. 

The  blood-vascular  system  is  in  the  form  of  a  nutritive  suppty;: 
the  larger  vessels  occupying  the  fibrous  framework,  and  sending 
branches  into  the  follicles.  The  capillary  plexuses  are  more  abun- 
dant in  the  peripheral  portion  of  the  follicles.  The  blood  is  col- 
lected in  the  venous  channels  of  the  central  or  medullary  area,  and 
emerges  from  the  organ  by  the  veins  which  accompany  the  efferent 
lymphatics. 

PRACTICAL   DEMONSTRATION. 

The  organ  should  be  obtained  from  a  still-born  infant,  divided 
in  small  pieces,  and  hardened  rapidly  in  strong  alcohol.  Sections 
may  include  an  entire  lobe,  and  be  stained  with  hsema.  and  eosin. 

SECTION  OF   THE   THYMUS   BODY  FROM  AN   INFANT 
AFTER  DEATH   ON  THE   SIXTEENTH  DAY. 

(Fig.  117.) 
OBSERVE: 

(L.) 

1.  The  fibrous  capsule. 

2.  Division  by  prolongations  of  1  into  somewhat  spherical 
lobes. 

3.  Subdivision  of  2  into  lobules. 

4.  Subdivision  of  3  into  follicles.     (Note  that  these  are  not 
uniformly  outlined  by  the  connective  tissue.) 

12 


178  PRACTICAL    MICROSCOPY. 

5.  The  subdivision  of  the  follicles  into   an   outer,  deeply- 
stained  cortex,  which  completely  surrounds  a  light  centre,  the 
medulla. 

6.  The  larger  lymph-spaces  and  arteries  of  the  capsular 
and  trabecular  tissue. 


FIG.  117.— SECTION  OP  A  PORTION  OF  THE  THYMUS  BODY,  FROM  A  CHILD,  SIXTEEN   DAYS 

AFTER  BIRTH.    X  60. 

A,  A.    Capsule  which  divides  the  organ  into  lobes.    Portions  of  six  lobes  are  visible  in  the 
section. 

B,  B.    Lymph-spaces. 

C,  C.    Trabeculae  dividing  the  lobes  into  imperfect  lobules. 

D,  D.    Subdivisions  of  the  last  into  follicles. 

E,  E.    Central  light  portion  of  the  lobules. 

(H.) 

7.  The  cortex  of  the  follicles,     (a)    The  numerous  deeply- 
stained  lymph-corpuscles,     (b)  The  network  of   the  adenoid 
tissue.     (This  will  be  greatly  obscured  by  the  lymphoid  cells.) 
(c)  The  blood  capillaries.     Only  recognized  by  the  contained  cor- 
puscles,    (d)  Minute  trabeculae  of  connective  tissue  projected 
from  the  capsule. 

8.  The  medulla  of  the  follicles,    (a)  The  sparsity  of  lymph- 
corpnscles  as  compared  with  the  cortical  portions,     (b)  Large 


SECTION    OF   THE   THYMUS   BODY.  179 

mononucleated  cells,     (c)  Still  larger  multinucleated  cells. 

(d)  Larger — though  varying  in  size — spherical  bodies,  HassaH's 
corpuscles.  (These  are  composed  of  epithelioid  cells,  arranged 
concentrically,  and  are  unlike  any  other  structure  found  in  the 
normal  tissues  of  the  body.  They  resemble  very  closely  the  smaller 
"  brood  nests "  of  epithelial  cancer.)  (e)  Small  thin-walled  ven- 
ules. 


180  PRACTICAL    MICROSCOPY. 

THE    NERVOUS    SYSTEM. 
STRUCTUKAL  ELEMENTS. 

The  elements  of  the  nervous  system  are : 
J.  Nerve  Fibres. 

2.  Nerve  Cells. 

3.  Connective  Tissue. 

4.  Peripheral  Termini. 

NERVE   FIBRES. 

A  typical  nerve  fibre  consists  of  three  portions,  viz. :  a  central 
conducting  portion,  the  axis  cylinder ;  the  medullary  sheath,  or 
white  substance  of  Scliwann  /  and  the  enveloping  connective-tissue 
substance,  the  neurilemma.  This  constitutes  a  medullated  nerve 
fibre,  and  is  found  largely  in  the  trunks  of  the  cerebro-spinal  sys- 
tem. The  trunks  of  the  sympathetic  system  are  composed  princi- 


FIG.  118.— SEPARATED  NERVE  FIBRES.     X  400. 

A.  Neurilemma  of  a  fibre. 

B.  White  substance  of  Schwann,  stained  with  osmic  acid,  which  hides  the  axis  cylinder. 

C.  Nucleus  of  the  neurilemma. 

D.  One  of  Ranvier's  nodes  in  an  osmic-acid  stained  fibre  showing  the  axis  cylinder  be- 
tween the  separated  portions  of  Schwann's  sheath. 

E.  A  medullated  fibre,  teased  in  normal  salt  solution.    The  medullary  substance  has  be- 
come coagulated  on  exposure  and  removal.    The  axis  cylinder  is  faintly  seen. 

F.  Axis  cylinder  at  torn  extremity. 

G.  Non-medullated  fibre. 

H.    Fibres  without  neurilemma.    Small  clusters  of  medullated  substance  are  seen  covering 
the  axis  at  irregular  intervals. 


NEKVE   CELLS.  181 

pally  of  fibres  destitute  of  the  white  substance  of  Schwann — 
non-medullated  nerves;  while  fibres  minus  the  neurilemma  exist 
in  the  trunks  belonging  to  some  organs  of  special  sense. 

After  treatment  with  reagents,  the  axis  cylinder  (one-two- 
thousand-five-hundredth  to  one-fifteen-thousandth  of  an  inch)  may 
be  split  up  longitudinally,  and  is  found  to  be  composed  of  fine 
(one-twenty-five-thousandth  of  an  inch)  primitive  or  ultimate 
fibrillaB,  which  present  minute  varicosities  or  swellings  at  irregular 
intervals. 

The  white  substance  of  Schwann  presents  under  the  microscope 
the  most  prominent  feature  of  inedullated  nerves,  affording  a 
nearly  complete  investment  of  the  nerve  axis. 

The  neurilemma  is  an  elastic  connective-tissue  envelope,  which 
completely  invests  the  medullary  substance.  This  tubular  mem- 
brane is  nucleated,  and  at  irregular  intervals  is  constricted  so  as  to 
reach  very  nearly  the  axis  cylinder.  These  constrictions  are  called 
by  Eanvier  nodes,  and  it  is  believed  that  the  perineurium  presents 
a  single  nucleus  between  each  of  these  nodal  points.  The  con- 
strictions do  not,  however,  affect  the  even  calibre  or  continuity  of 
the  axis  cylinder. 

A  typical  nerve  fibril  has  been  described  as  resembling,  struc- 
turally, a  doubly  insulated  telegraphic  cable,  but  the  comparison  is 
unfortunate  and  misleading,  as  the  functioning  of  the  nerve  bears 
no  resemblance  to  the  phenomena  exhibited  by  electrical  con- 
ductors. 

NERVE   CELLS. 

Nerve  cells  are  usually  grouped,  and  are  the  essential  feature  of 
nerve  centres,  otherwise  called  ganglia  or  gray  matter.  Ganglion 
cells  are  among  the  largest  cell  elements  of  the  body,  and  consist 
of  a  dense,  reticulated,  and  frequently  pigmented  ground  work, 
inclosing  a  large  translucent  nucleus,  and  usually  a  single  nucle- 
olus.  One  or  more  prolongations,  poles  or  horns,  are  sent  from 
these  cells,  and  hence  they  have  been  classified  as  unipolar,  bipolar, 
tripolar,  quadripolar,  and  multipolar,  according  to  the  number  of 
projections.  The  cell  prolongations  generally  divide  soon  after 
leaving  the  body,  and  subdivision  continues  until  exceedingly 
minute  fibrils  result,  which  serve  as  connecting  links  of  the  ele- 
ments of  a  ganglion.  Usually  one  (the  larger)  pole  is  projected 
which  remains  unbranched.  This  becomes  the  axis  cylinder  of  a 
nerve  fibril,  and  affords  connection  between  the  elements  of  a  gan- 
glionic  centre  and  the  conducting  portion  of  the  nervous  apparatus. 


182  PRACTICAL    MICROSCOPY. 

Ganglion  cells  are  surrounded  by  irregular  channels  or  lymph- 
spaces,  and  are  thus  in  intimate  relation  with  the  lymphatic  system. 


CONNECTIVE   TISSUE  OF   THE   NERVOUS   SYSTEM. 

The  connective  tissue,  which  serves  to  unite  the  elements  of  a 
nerve  trunk,  does  not  differ  materially  from  the  sustentacular  tis- 
sue of  other  organs.  Different  terms  are  applied,  according  to  its 
use  and  location,  as  follows : 

EPINEURIUM. — Forming  the  sheath  of  the  entire  nerve  trunk. 

PERINEURIUM. — Surrounding  the  bundles  composing  the  nerve 
trunk. 

ENDONEURIUM. — Permeating  and  uniting  the  elements  of  the 
bundles. 


FIG.  119.— TRANSVERSE  SECTION  OF  THE  ANTERIOR  CRURAL  NERVE,     x  250. 

A.  The  epineurium. 

B.  Adipose  tissue  in  the  loose  areolar  tissue  of  the  sheath. 

C.  Lymph-spaces  of  the  epineurium. 

D.  Large  blood-vessels  of  epineurial  sheath. 

E.  Perineurium  surrounding  nerve  bundles. 

F.  Lymph-spaces  of  last. 

G.  Medulkited  nerves  in  T.  S.  supported  by  connective  tissue — endoneurium. 


NEUROGLIA.  183 

NEURILEMMA. — Surrounding  the  individual  nerve  fibres  of  a 
bundle. 

The  formula  E.  P.  E.  N.,  composed  of  the  initial  of  the  name 
of  the  investments  from  without  inward,  will  aid  the  memory. 

The  epineurium  serves  to  protect  the  organ  in  its  passage,  and 
to  support  the  nutrient  blood-vessels  and  the  channels  of  lymphatics. 
The  fibres  run  both  longitudinally  and  transversely.  The  perineu- 
rium,  arranged  in  dense  bands,  forms  distinct  sheaths  for  the  nerve 
bundles,  the  fibres  running,  for  the  most  part,  circularly.  The 
endoneurium  not  infrequently  divides  the  nerve  bundles  into 
smaller  or  primitive  bundles.  It  supports  the  blood  capillaries, 
contains  small  lymph-spaces,  and  its  nuclei  are  frequently  large 
and  prominent. 

The  final  distribution  of  the  elements  of  a  nerve  trunk  is 
effected  by  subdivision;  first,  of  the  large,  and  afterward  of  the 
primitive  bundles  or  fasciculse.  The  perineurial  sheaths  are  pro- 
longed, furnishing  the  dividing  bundles,  even  to  the  final  distribu- 
tion, where,  around  terminal  and  single  medullated  fibres,  the 
sheath  remains  as  a  layer  of  exceedingly  delicate  flattened  cells. 
The  necessity  for  the  endoneurium  ceases  with  the  ultimate  sub- 
division of  the  nerve  fasciculus. 

NEUROGLIA. 

The  sustentacular  or  supporting  tissue  of  the  brain  and  spinal 
cord  differs  materially  from  ordinary  connective  tissue.  It  pre- 


FIG.  120.— NEUROGLIA,  FROM  BENEATH  THE  PIA  MATER  OP  THE  SPINAL  CORD.    X  400. 

A.  Network  of  neuroglia  fibrils. 

B.  Spider  (Deiter's)  cells. 

C.  Nerve  fibres  in  T.  S. 


184  PRACTICAL    MICROSCOPY. 

sents  an  interlacement  of  fibres  which,  even  with  the  highest  powers 
of  the  microscope,  appear  of  exceeding  tenuity.  The  neuroglia 
mesh  supports  the  nervous  elements,  scattering  branched  (Deiter's) 
cells,  and  small  round  cells. 

Peripheral  Termini.  (The  demonstration  of  peripheral  nerve 
apparatus  should  not  be  attempted  until  additional  work,  in  the 
lines  hereafter  indicated,  has  secured  for  the  student  a  degree  of 
perfection  in  technique  which  he  is  not  at  present  supposed  to 
possess.) 


SPINAL   COUD, 


SPINAL  CORD. 

The  membranes  covering  the  cord  will  be  discussed  later. 

The  spinal  cord  is  composed  of  gray  (cellular)  and  white 
(fibrous)  nerve  matter,  and  serves  as  a  medium  of  communication 
between  the  brain  and  peripheral  nerve  apparatus.  The  arrange- 
ment of  its  several  parts  will  be  best  understood  by  the  study  of  a 
transverse  section,  of  which  Fig.  121  is.  a  diagrammatic  representa- 
tion. 

The  gray  substance  occupies  the  central  portions  of  the  struc- 
ture, and  consists  of  two  lateral  masses  and  a  connecting  link  or 
commissure,  Near  the  central  portion  of  the  figure,  a  small  circu- 


FIG.  121.— DIAGRAM.    CERVICAL  SPINAL  CORD  IN  TRANSVERSE  SECTION. 

A.  Anterior  median  fissure. 

B.  Posterior  median  fissure. 

C.  Anterior  cornu — gray  substance. 

D.  Posterior  gray  cornu. 

E.  Point  of  emergence  of  anterior  root  of  spinal  nerve. 

F.  Posterior  root  of  spinal  nerve. 

G.  White  commissure. 

H.  Anterior  gray  commissure. 
I.  Posterior  gray  commissure. 
J.  Substantia  gelatinosa. 

The  tracts  which  are  named  on  the  diagram  have  no  definite  boundaries  histologically. 
'They  are  physiological  areas. 


186  PRACTICAL     MICROSCOPY. 

lar  opening  presents — the  transversely  divided  central  canal.  This 
is  in  communication,  in  the  medulla,  with  the  fourth  ventricle, 
and  will  serve  as  a  starting-point  for  our  study. 

The  gray  matter  completely  surrounds  the  central  canal,  and 
its  outline  resembles  the  capital  H.  The  bars  or  columns  each 
present  anteriorly  a  blunted  extremity,  horn  or  connt,  while  the 
posterior  cornua  are  pointed.  The  lateral  bars  or  columns  are  con- 
nected, as  we  have  seen,  a  portion  of  the  connecting  substance  pass- 
ing in  front  and  a  portion  behind  the  central  canal— -tf/je  anterior 
and  posterior  gray  commissural  bands. 

The  white  substance  is  divided  anteriorly  by  the  anterior  median 
fissure,  which  sections  the  cord  nearly,  but  not  entirely,  to  the-, 
anterior  gray  commissure.  A  corresponding  division  appears 
posteriorly  (the  posterior  median  fissure)  which  does  not  divide  the 
cord  posteriorly  as  completely  as  does  the  previously-named  fissure 
anteriorly;  but  the  division  is  indicated  by  a  band  of  neuroglia, 
which  penetrates  entirely  to  the  posterior  gray  commissure.  The 
two  masses  of  white  substance  thus  indicated  by  more  or  less  com- 
plete central  division  are  termed  lateral  white  columns,  and  these- 
are  united  just  in  front  of  the  anterior  gray  commissure  by  white 
nerve  tissue — the  white  commissure.  The  spinal  nerves  take  origin 
from  the  gray  cornua,  the  anterior  roots  from  the  anterior  and  the 
posterior  roots  from  the  posterior  cornua.  The  white  substance 
consists  essentially  of  medullated  fibres  which,  with  the  exception 
of  the  anterior  spiral  nerve  roots  and  the  commissural  fibres,  pass. 
mainly  in  a  longitudinal  direction. 

PRACTICAL   DEMONSTRATION. 

Nerve  tissue  should,  under  all  circumstances,  be  hardened  in 
Miiller's  fluid.  The  cord  should  be  obtained  as  nearly  fresh  and 
uninjured  as  possible;  cut  transversely  with  a  sharp  razor  into- 
pieces  half  an  inch  long,  and  placed  immediately  in  the  fluid — in 
the  proportion  of  a  pint  of  the  mixture  to  two  ounces  of  tissue. 
The  solution  should  be  thrown  away  after  twenty-four  hours,  and 
a  fresh  supply  provided.  It  should  be  again  changed  after  three 
days,  and  again  after  another  week.  After  four  weeks  the  bi- 
chromate should  be  poured  off,  and  the  tissue  rinsed  once  with 
water;  after  which  the  hardening  is  to  be  completed  with  alcohol 
in  the  ordinary  manner — i.e.,  commencing  with  the  weak  spirit. 

After  hardening,  pieces  from  the  different  regions  should  be- 
cut,  and  this  is  best  effected  by  the  infiltration  methods.  Trans- 
verse sections  are  the  most  instructive,  although  the  student  should 
afterward  study  longitudinal  cuts.  The  sections  must  be  thin,  but 
not  necessarily  large,  and  they  may  be  stained  by  the  method  of 


HUMAN   SPINAL   CORD.  187 

Weigert,  or  with  haema.  and  eosin.  Weigert's  method  requires 
very  careful  manipulation,  and  is  of  more  special  value  in  patho- 
logical research. 

If  human  tissue  cannot  always  be  procured  in  suitable  condi- 
tion, the  cord  of  the  ox,  pig,  sheep,  cat,  or  rabbit  will  serve  well. 
The  ox,  especially,  provides  a  means  of  securing  tissue  of  surpass- 
ing excellence,  particularly  for  demonstration  of  the  ganglion  cells. 
The  cord  of  the  smaller  domestic  animals  is,  in  nearly  every  re- 
spect, as  valuable  for  study  as  that  of  man,  especially  as  the  latter 
cannot  usually  be  gotten  before  the  serious  putrefactive  changes., 
to  which  nerve  tissue  is  prone,  have  made  marked  progress. 

HUMAN   SPINAL   CORD.     CERVICAL   REGION. 

TRANSVERSE    SECTION.      (Fig.  122.) 

OBSERVE: 

(L.) 

1.  General  arrangement  of  gray  and  white  substance,  with 
the  latter  surrounding  the  former,  which  resembles  in  outline  the 
letter  H. 

2.  Subdivisions  of  white  substance,     (a)  Anterior  median 
fissure.     (Note  its  passage  inward  and  its  cessation  before  reach- 
ing the  gray  substance.)     (b)  Posterior  median  fissure.     (Note 
its  shallowness  as  a  true  fissure,  and  the  extension  of  the  connective 
tissue  from  the  bottom   inward,  until  the  gray  substance  is  met. 
Compare  the  two  median  fissures.)     (6')  The  emergence  of  the  an- 
terior nerve-roots.      (This  provides  the  external  or  lateral  bound- 
ary of  anterior  white  columns  or  direct  pyramidal  tracts,  the  in- 
ternal boundaries  being  provided  by  the  anterior  median  fissure.) 
(d)  The   lateral    columns.      (These   contain   the   fibres   of  the 
crossed  pyramidal  tract,  and  include  the  white  substance  between 
the  anterior  nerve-roots  and  the  posterior  gray  cornu.     Each  lat- 
eral column  contains  nerve  fibres  which  pass  to  the  cerebellum — 
direct  cerebellar  tract;    observe  that  these  tracts  have  no  internal 
histological  boundary.     Note  the  numerous  prolongations  of  the- 
pia  mater  inward  in  the  lateral  columns.)     (e)  The  postero-internal 
or  column  of  Goll  -funiculus  gracilis.     (These  columns  present 
on  either  side  of   the  posterior  median  fissure,  and  are  bounded 
laterally  by  a  prolongation  from  the  pia  mater.)    (/)  The  postero- 
external  columns— funiculus  cuneatus.     (Bounded  internally  by 
the  postero-internal  columns,  and  externally  by  the  posterior  gray 
cornua.)     (g)  The  white  commissure.     (Note  the  absence  of  a 
white  commissure  posteriorly,  the  posterior  median  septum  reach- 
ing the  gray  substance.) 


188 


PRACTICAL    MICROSCOPY. 


3.  Subdivisions  of  the  gray  substance,  (a)  The  central 
canal.  (Should  the  section  have  been  taken  from  the  extreme 
lower  cervical  cord,  this  canal  as  such  will  be  difficult  of  demon- 
stration, a  number  of  deeply-stained  cells  only  remaining.)  (b) 
The  gray  commissure,  anterior  and  posterior,  (c)  The  gray 
columns,  (d)  The  anterior  gray  cornua,  broad  and  not  reach- 
ing the  periphery  of  the  cord  section,  (e)  The  posterior  cornua, 
narrow  and  passing  completely  out,  posteriorly,  to  form  the  pos- 
terior root  of  a  spinal  nerve. 


FIG.  122.—  TRANSVERSE  SECTION  OP  THE  SPINAL  CORD.    MIDDLE  CERVICAL  REGION.    X  60. 

A.    Anterior.  B.    Posterior 

The  references  in  Fig.  131  apply  also  to  this  illustration.    Also  vide  text. 
This  section  was  made  from  the  cord  of  a  man  who  died  at  the  age  of  75  years,  from  senile 
dementia.    The  gray  substance  is  perfectly  normal,  but  of  somewhat  diminished  area. 


4.  The  white  substance  (select  a  field,  e.g.,  in  the  anterior 
median  column,  and  observe  the  transversely-divided  nerves),  (a) 
The  nerves  are  not  collected  into  fasciculae,  but  each  fibre  pur- 
sues an  independent  course,  (b)  The  axis  cylinders,  stained 
lightly  with  the  eosin.  (Note  the  great  variation  in  size.)  (c) 
Most  of  the  axis  cylinders  surrounded  by  more  or  less  concentric 


HUMAN    SPINAL    CORD. 


189 


rings  of  translucent,  unstained  white  substance  of  Schwann, 
(These  are  medullated  fibres.)  (d)  The  few  and  scattering  axis 
cylinders  without  surrounding  white  substance.  (Non-medullated 
nerves.)  (e)  The  neurilemma,  appearing  as  a  thin,  violet  ring 
around  the  white  substance  of  Schwann.  (Most  medullated  nerves 
of  the  cerebro-spinal  system  are  provided  with  this  sheath.)  ( f) 
The  small,  about  one-tliree-thousandth  of  an  inch,  deeply  haema.- 
stained  cells  of  the  neuroglia.  (g)  The  neuroglia  substance, 
finely  granular  or  fibrillated,  between  the  nerve  fibres,  (li)  The 
spider  cells  (Deiter's)  of  the  neuroglia.  (These  are  not  numer- 
ous, but  easily  found  near  the  periphery.)  (i)  The  longitudinal 


FIG.  123.— SAME  SPECIMEN   AS  SHOWN  IN  FIG.  122.    MORE  HIGHLY  MAGNIFIED.    REGION  OF 
ANTERIOR  CORNU.     X  350. 

A.  Medullated  filaments  passing  out  from  the  gray  substance  to  form  the  anterior  root 
of  a  spinal  nerve. 

B.  Ganglion  cells. 

C.  Neuroglia  nuclei. 

D.  Blood-vessels. 

E.  One  of  the  transversely  divided  medullated  fibres  of  the  white  substance,  anteriorly  to 
the  anterior  gray  cornu.    The  line  leads  to  the  neurilemma. 

F.  White  substance  of  Schwann— of  last. 

G.  The  axis  cylinder  of  E. 

nerve  fibres  passing  from  the  anterior  gray  cornu  to  form  the 
anterior  root  of  a  spinal  nerve.  (/)  The  different  size  of  the 
nerve  fibres  in  different  areas  of  the  section.  (Note  the  small 
fibres  of  the  postero-internal  column.)  (k)  The  blood-vessels. 
(These  vessels  are  largely  confined  to  the  neuroglia-septa,  which 


190  PRACTICAL    MICROSCOPY. 

pass  in  from  the  pia.     These  septa  contribute  to  the  formation  of 
the  nearest  approach  afforded  by  the  cord  of  nerve  bundles.) 

5.  The  gray  substance,  (a)  The  central  canal.  (The 
canal  is  lined  with  columnar  ciliated  cells  in  single  layer.  The 
cilia  are  rarely  demonstrable  in  the  human  cord,  on  account  of 
changes  which  occur  very  quickly  after  death.  The  canal  is  usually 
broadest  in  its  lateral  diameter,  viz.,  at  upper  portion  of  cervical 
region,  from  one-one-hundredth  to  one-two-hundredth  of  an  inch. 
{b)  The  ground  substance.  (This  consists,  1st,  of  exceedingly 
minute  fibres,  formed  by  the  repeated  subdivision  of  the  axis  cylin- 
ders—the primitive  fibrillae  ;  2d,  of  the  delicate  neuroglia  fibres. 
It  is  usually  difficult  in  a  section  to  differentiate  between  the  two. 
Attempts  have  been  made,  with  more  or  less  success,  to  differenti- 
ate by  means  of  staining  agents.)  (c)  Large  ganglion  cells. 
(Select  a  field  in  the  anterior  horn.  The  straight,  unbranchiiig 
axis-cylinder  process  can  frequently  be  distinguished.  Note  the 
large,  shining  nucleus  and  the  deeply- stained  nucleolus.  These 
cells  are  frequently  deeply  pigmented.)  (d)  Small  ganglion  cells. 
(Best  seen  in  the  posterior  horn.  In  the  dorsal  cord  a  collection 
of  medium-sized  cells  presents,  just  within  the  posterior  commis- 
sure and  encroaching  upon  the  white  substance  posteriorly  to  this, 
the  column  of  Lockhart  Clarke.)  (e)  Lymph  spaces.  (Observed 
as  a  somewhat  clear  space  around  the  ganglion  cells.)  (/)  Blood- 
vessels. (These  are  much  more  numerous  here  than  in  the  white 
portion;  and  arteries  may  frequently  be  found  of  considerable 
size.)  (g)  Peri-vascular  lymphatics.  (Find  an  artery  in  trans- 
verse section,  and  observe  the  clear  space  around  it,  which  may  be 
mistaken  for  the  result  of  contraction  of  the  tissue  in  hardening. 
Careful  study  will  reveal  minute  branches  of  cells,  passing  between 
the  adventitia  of  the  blood-vessel  and  the  wall  of  the  lymph  space.) 


THE   BlJAIJf    AND   ITS    JIEM13KA1MES.  191 


THE    BRAIN  AND   ITS   MEMBRANES. 

The  brain  and  spinal  cord  are  surrounded  by  three  connective- 
tissue  layers — the  dura  mater,  arachnoid,  and  the  pia  mater. 

The  dura  is  the  most  external  and  the  thickest  of  the  three 
membranes,  and  constitutes  the  periosteal  lining  of  the  cranial  and 
spinal  cavities.  It  consists  largely  of  elastic  tissue,  the  laminae 
and  blood-vessels  of  which  are  supported  by  connective  tissue. 
The  outer  surface  is  in  more  or  less  intimate  connection  with  the 
bone,  and  both  surfaces  are  covered  with  a  single  layer  of  thin  pave- 
ment cells.  Beneath  is  a  space — the  subdural — containing  lymph. 

The  arachnoid,  exceedingly  thin,  presents  an  outer,  glistening, 
pavement-cell  covered  surface  (isolated  from  the  dura  by  the  sub- 
dural space),  from  the  under  (inner)  side  of  which  short  fibrous 
trabeculae  are  projected  to  the  pia.  The  subaracJmoiclal  space  is 
thus  seen  to  consist  of  numerous  communicating  chambers,  and 
these  spaces  are  everywhere  lined  with  flat  cells,  and  contain  lymph, 
as  does  the  subdural  space. 

The  pia  mater  consists  of  fibrillated  connective  tissue,  usually 
in  intimate  connection  with  the  arachnoid  externally,  by  means  of 
the  trabeculae  of  the  latter.  The  pia  is  exceedingly  vascular,  and 
everywhere  covers  the  brain  and  cord,  and,  unlike  the  arachnoid, 
penetrates  the  sulci  of  the  former  and  the  fissures  of  the  latter, 
becoming  continuous  with  the  neuroglia  tissue. 

The  subdural  and  subarachnoidal  spaces  are  lymph-cavities,  and, 
while  not  in  direct  connection  one  with  the  other,  belong  to  the 
general  lymphatic  system,  and  are  in  eventual  connection.  The 
two  spaces  are  projected,  independently,  in  the  sheaths  of  the 
cranial  and  spinal  nerves — the  subdural  communicating  with  the 
lymph  channels  of  the  epineurium,  and  the  subarachnoidal  with 
those  of  the  perineurium. 

The  arrangement  of  gray  and  white  nerve  substance  in  the 
brain  is  precisely  the  reverse  of  that  of  the  cord.  The  gray  mat- 
ter forms  an  external  covering  or  layer  of  varying  thickness,  while 
the  white  matter  occupies  the  more  central  regions.  Collections  of 
gray  matter — ganglia — are  also  situate  in  the  deeper  parts  of  the 
brain  substance,  the  study  of  which  does  not  come  within  the 
limits  of  this  work. 

The  brain  substance  does  not  differ,  essentially,  from  the  cord, 
except  in  the  arrangement  of  its  parts.  The  nerve  fibres  are  largely 


192  PRACTICAL    MICROSCOPY. 

medullated,  but  have  no  neurilemma.  The  neuroglia  and  gan- 
glionic  tissues  do  not  here  differ  in  structure  from  that  previously 
described.  The  gray  substance  is  arranged  in  layers,  which  are, 
in  some  instances,  quite  sharply  denned,  and  again  demonstrabla 
only  with  considerable  difficulty. 

PRACTICAL   DEMONSTRATION. 

The  tissue  is  to  be  prepared  in  the  manner  usual  with  nerve 
substance — hardened  with  Miiller,  followed  b}^  alcohol.  Thin  sec- 
tions, stained  deeply  with  haema.  and  eosin,  may  be  mounted  in 
dammar  or,  if  preferred,  in  glycerin. 

SECTION   OF   HUMAN    CEREBRUM.     CUT    PERPENDIC- 
ULARLY  TO   THE   SURFACE.      (Fig.  124.) 
OBSERVE: 

(I.)' 

1.  The  membranes.  (In  the  drawing  only  the  arachnoid  and, 
pia  are  shown.)     (a)  The  fine  fibrillar  mesh  of  the  arachnoid, 
(b)  The  nuclei  of  the  flattened  cell-covering,     (c)  The  large 
blood-vessels,     (d)    The  pia.     (e)    Its  continuity   with  the 
neuroglia  of  the  cerebrum. 

2.  The  outer  layer — the  first — of  the  gray  substance.     (This 
layer  is  poorly  defined,  but  can  usually  be  made  out.  •   It  consists 
of  primitive  nerve  fibrillse,  neuroglia  fibrils,  and  scattered  spher- 
ical cells.) 

3.  The  second  layer.     (This  layer  presents  about  the  same 
thickness  as  the  preceding,  and  will  be  recognized  by  the  numerous 
small,  triangular  nerve-cells.     Indeed,  these  afford  the  only  means, 
of  distinguishing  the  boundary  between  the   two  layers,  as  the 
stained  elements  of  the  outer  layer  are  seldom  pyramidal.) 

4.  The  third  layer.     (This  layer — the  thickest  of  all  the  gray 
laminae — has  been  shortened  in  the  drawing,  on  account  of  lack  of 
space.     It  is  three  or  four  times  as  thick  as  the  first  layer,  and  will 
be  readily  made  out  by  the  large,  elongate,  pyramidal  cells,  with 
their  long  axes  at  right  angles  to  the  brain  surface.     Medullated 
fibres,  in  more  or  less  distinct  bundles,  pass  between  the  column- 
like  ganglion  cells.) 

5.  The  fourth  layer.     (The  large  cells  of  the  third  layer  are 
seen  to  stop  abruptly,  as  we  pass  inward,  and  give  place  to  small, 
triangular  nerve-cells.     This  brings  us  to  the  fourth  plane.     Be- 
tween the  cells  of  this  layer,  bundles  of  nerve-fibres  are  seen,  a& 
they  radiate  toward  the  cerebral  surface.) 


THE   BRAIN   AND   ITS   MEMBRANES. 


193 


6.  The  fifth  layer.     The  line  of  demarcation  between  this  and 
the  fourth  layer  is  feebly  shown ;  but,  on  close  attention,  it  will  be 
observed  that  the  small  cells  of  the  fourth  layer  rather  abruptly 
give  place  to  elongate  ones,  not  unlike  those  of  the  third  stratum. 
The  nerve-bundles  are  here  more  plainly  indicated. 

7.  The  white  matter.     (The  ganglion  cells  here  cease,  and 
the  field  is  occupied  with  medullated  fibres  and  neuroglia,  the 


FIG.  124.— VERTICAL  SECTION  OF  CEREBRAL  CORTEX.    SUPERIOR  FRONTAL  CONVOLUTION. 

X  250. 

A.  Arachnoid. 

B.  Pia  mater. 

C.  D,  E,  F,  G.    First,  second,  third,  fourth,  and  fifth  layers  of  gray  matter. 
H.    White  brain  substance. 


spherical  nuclei  of  the  latter  becoming  prominent  from  the  deep 
haema.  staining.) 

8.  The  nutrient  blood-vessels.  (The  capillaries  projected 
from  the  pia  are  especially  to  be  noticed,  often  of  the  diameter  of 
a  single  blood -corpuscle,  and  presenting  as  branching  lines,  com- 
posed of  these  elements — indeed  difficult  of  demonstration  when 
empty.  Note  the  light,  perivascular  lymph-spaces,  well  seen, 
around  the  larger  arteries  in  transverse  section.) 
13 


194 


PEACTICAL    MICROSCOPY. 


VERTICAL  SECTION   OF   HUMAN    CEREBELLUM. 
PREPARED   AS   LAST   SPECIMEN. 

(Figs.  125  and  126.) 
OBSERVE: 

(L.) 

1.  The  arrangement  of  the  cortex  in  the  form  of  leaflets. 

2.  The  extension  of  the  gray  laminae  within  even  the  mi- 
nutest folds  of  the  leaves,  so  as  to  completely  envelop  the  central 


FIG.  125.— LONGITUDINAL  SECTION  OF  ONE  OF  THE  FOLIA  OF  THE  CEREBELLUM.    X  60. 

A,  A.    Line  of  pia  mater. 

B,  B.    Sulci. 

C,  C.    Outer  layer  of  gray  matter. 

D,  D.    Inner  layer  of  gray  matter,  including  Purkinje's  cells. 

E,  White  nerve  substance. 

white  nerve-substance.  (The  staining  has  been  so  selected  by  the 
tissue  as  to  divide  the  outer  gray  matter  into  two  prominent  layers. 
The  explanation  of  this  will  follow  increased  amplification.) 

3.  The  central  white  matter.     (The  fibrillar  character  can 
be  made  out,  and  the  general  plan  seen  to  consist,  as  in  the  cere- 


VERTICAL    SECTION    OF    HUMAN    CEREBELL 

brum,  of  central  nerve  fibrillae  radiating  toward  the  cells  of  the 
cortical  gray  substance.) 

(H.) 

4.  The  outer  gray  layer.  (This  is  the  thickest  of  the  three 
layers.  The  prominent  elements  to  be  observed  are :  the  scatter- 
ing spherical  neuroglia  and  small  nerve-cells,  nerve-fibrils 
passing  at  right  angles  to  the  surface  and  lost  as  the  outer  region 
is  approached,  the  prominent  blood-vessels  which  pass  in  from 
the  pial  investment.) 


FIG.  126  —VERTICAL  SECTION,  CORTEX  OF  CEREBELLUM.    PORTION  OF  SECTION  SHOWN  IN  FIG. 
125,  MORE  HIGHLY  MAGNIFIED,     x  250. 

A.  Outer  layer  of  gray  matter. 

B.  Layer  of  Purkinje's  cells. 

C.  Inner  gray  layer. 

D.  White  nerve  substance. 

5.  The  ganglionic  layer.  (Directly  beneath  the  outer  layer 
the  section  becomes  deeply  stained,  from  the  presence  of  numer- 
ous small  cells,  among  and  partly  concealed  by  which  are  the  large 
ganglion  cells  of  Purkinje.  These  are  flask-shaped,  and  are 
arranged  in  a  single  plane,  with  their  long  axes  vertically.  A 


196  PRACTICAL    MICROSCOPY. 

thread-like  prolongation  may  be  seen  penetrating  the  layer  be- 
neath, providing  the  cell  has  been  centrally  sectioned.  Large 
horns  are  projected  from  the  outer  extremity  of  the  cells, 
branches  from  which  provide  the  nerve-fibrils  seen  in  the  last- 
observed  layer.  The  cells  bodies  take  the  eosin,  and  the  nuclei 
the  logwood.) 

6.  The  granular  layer.     (This  is  the  layer  seen  so  distinctly 
with  the  low  power.     It  consists  of  innumerable  small,  deeply 
hasma.-stained  bodies,  usually  spherical,  which  are,  as  is  believed, 
mostly  neuroglia  cells.     These  nucleated  elements  are  imbedded 
in  an  exceedingly  fine  matrix  of  neuroglia  [Klein]  fibrils.     Search 
carefully  for  the  axis  cylinder  processes  of  the  Purkinje  cells 
which  pierce  this  layer,  and  follow  them  into  the  white  matter 
below.) 

7.  The  white  substance.    (This  consists  of  medullated  nerves 
which  arise  largely  from  the  cells  of  the  second  gray  layer.     Klein 
has  also  traced  fibres  into  the  nuclear  la}rer,  and  demonstrated  their 
distribution  to  the  small  ganglion  cells  of  the  lamina,  and  to  the 
network  of  the  outer  gray  substance.) 


FORMULAE.  197 

MISCELLANEOUS  FORMULAE. 
D4MMAR   MOUNTING   VARNISH. 

No.  I. 

Gum  dammar,     .         .         .         .        „..       .  4  ounces. 

Gum  mastic  (in  "tears"),  .         .        ,         .  2       Cf 

Spirits  of  turpentine, 8       " 

Chloroform  (Squibb's),       ....  4       " 

Mix  the  dammar  with  about  an  equal  bulk  of  clean  broken 
glass.  Put  in  a  wide-mouth  bottle,  and,  having  added  the  turpen- 
tine, set  in  a  warm  place.  The  glass  is  added  for  the  purpose  of 
separating  the  lumps  of  the  resin,  and  thus  hastening  the  solution. 
Stir  the  mixture  occasionally. 

Add  the  mastic  to  the  chloroform  in  a  well-stoppered  bottle. 

When  the  solution  of  the  resins  is  complete,  add  the  chloroform 
mixture  to  the  dammar,  and  keep  in  a  bottle  covered  with  a  plate 
of  glass.  After  the  dirt  from  the  gum  has  thoroughly  settled, 
decant  into  small  bottles  for  use.  Do  not  attempt  to  filter. 

I  have  histological  mounts  which  were  made  with  this  medium 
nearly  ten  years  since,  and  the  tissues  have  shown  no  deterioration 
whatever. 

DAMMAR    MOUNTING   VARNISH. 

No.  2. 

Best  dammar  varnish  of  the  paint-shops,  diluted  with  a  suffi- 
cient quantity  of  turpentine. 

I  do  not  know  that  this  is  in  any  way  inferior  to  the  last,  but 
histologists  generally  have  a  preference  for  media  of  known  com- 
position. They  may  both  be  diluted  with  turpentine,  chloroform, 
ether,  or  pure  benzole  ;  or  thickened,  by  removing  the  stopper  of 
the  bottle  until  a  sufficient  amount  of  the  solvent  has  evaporated. 

XYLOL   BALSAM. 

Xylol  is  preferred  by  some  histologists  as  a  solvent  or  diluent 
of  Canada  balsam  for  general  mounting  purposes.  Xylol  dissolves 
the  balsam  very  readily  without  heat,  and  evaporates  more  rapidly 
than  most  solvents.  A  thin  solution — say  xylol  two  parts  to 


198  PRACTICAL  MICROSCOPY. 

Canada  balsam  one  part— should  be  first  prepared,  and,  after  filter- 
ing through  paper,  it  may  be  placed  in  an  unstoppered  bottle  until, 
by  evaporation,  it  becomes  sufficiently  thick  for  use. 

Xylol  is  miscible  with  strong  alcohol,  oil  of  cloves,  etc.,  but  not 
with  water. 


VARNISHES   AND   CEMENTS   FOR  RINGING   MOUNTS. 

1.  Dammar. — I  believe  a  clean  dammar  mount,  with  circular 
cover,  neatly  labelled,  cannot  be  improved  in  appearance  by  paint- 
ing rings  of  colored  varnish  around  the  specimen.     Nevertheless, 
the  beginner  will  purchase  and  use  a  turn-table,  and  must  be  there- 
fore directed  in  its  employment. 

A  ring  of  dammar,  thinned  with  turpentine  so  as  to  flow  read- 
ily from  the  brush,  makes  a  very  neat  border  to  the  cover-glass  of 
a  specimen  mounted  in  this  medium.  Let  the  layer  be  quite  thin. 

2.  Zinc  Cement. — To  a  small  quantity  of  thin  dammar  varnish, 
add  q.  s.  of  pure  dry  zinc  white.     Mix  thoroughly  on  a  glass  plate 
with  paint-knife  or  spatula.     The  consistency  should  be  such  as  to 
flow  readily  from  the  brush. 

Before  adding  any  cement  containing  pigment  or  color  to  a 
dammar  mount,  a  protecting  covering  should  be  applied;  otherwise 
the  cement  will  eventually  creep  in  between  the  cover  and  the  slide 
and  mix  with  the  original  mounting  varnish.  It  may  proceed  very 
slowly;  but  in  time  the  specimen  will  be  surely  ruined.  This  is 
best  avoided  by  painting  a  thin  ring  around  the  edge  of  the  cover 
of  liquid  glue.  Cooper's  and  LePage's  are  both  excellent.  Let 
this  dry,  and  any  amount  of  varnish  may  be  subsequently  applied 
without  disaster. 

Aniline  Colors.  Red,  blue,  etc.,  may  be  employed  by  dissolving 
the  dry  color  in  a  little  thin  shellac  varnish.  This  dries  quickly 
and  may  be  used  over  the  zinc. 

Oil  colors.  The  artists'  colors  which  are  sold  in  tubes  may  be 
thinned  with  dammar. 

Black  varnish.  This  is  the  "  Black  Japan  "  of  the  paint  shops. 
It  may  be  made  by  dissolving  gum  asphaltum  in  turpentine.  The 
genuine  asphaltum  is  very  difficult  to  procure,  as  coal  tar  is  gener- 
ally sold  under  this  name.  It  is  therefore  best  to  purchase  the 
varnish,  thinning  with  turpentine  or  pure  benzol  if  necessary. 

Shellac  Varnish. — The  best  orange  shellac  dissolved  in  strong 
alcohol,  in  quantity  sufficient  to  make  a  varnish  of  the  consistency 
of  treacle. 


FORMULAE.  199 

This  is  an  excellent  cement  for  glycerin  mounts.     It  should  be 
considerably  thinned  for  use  as  a  vehicle  for  color. 


PRESERVATIVE   FLUID. 

Acetate  of  soda, 1  pound. 

Distilled  water,  ......     8  ounces. 

Scrapings  or  teasings  from  tissues,  morphological  elements  from 
urinary  sediment,  casts,  in  fact,  almost  any  histological  element 
may  be  indefinitely  preserved  in  this  solution.  It  is  important 
that  the  tissues,  etc.,  be  freed  from  organic  matters  in  solution, 
before  being  placed  in  the  preservative ;  for  example :  urine  must 
be  carefully  decanted  from  the  sediment  to  be  preserved  before  the 
acetate  solution  is  added.  I  am  enabled  to  preserve  the  different 
forms  of  cells  from  year  to  year,  for  my  classes,  in  small  bottles  of 
this  fluid.  When  a  demonstration  is  required,  it  is  simply  neces- 
sary to  transfer  a  drop  of  the  sediment,  by  means  of  a  pipette,  to 
a  slide,  and  apply  the  cover-glass, 

If  it  be  desired  to  preserve  such  a  mount,  wipe  the  edges  of  the 
cover  with  a  bit  of  blotting-paper,  and  seal  with  a  ring  of  shellac 
or  asphaltum  varnish,  or  zinc  cement,  applied  with  a  small  brush. 

NORMAL  SALT   SOLUTION. 

Chloride  of  sodium  (common  salt),  .     7  grains. 
Distilled  water, 2  fluid  ounces. 

A  medium  for  the  temporary  examination  of  fresh  tissues — 
scrapings,  teasings,  etc. 

RAZOR-STROP   PASTE. 

Sulphate  of  iron  and  common  salt  equal  parts.  Calcine  in  a 
sand  crucible  at  a  dull  red  heat  for  ten  minutes.  When  cold, 
grind  lightly  in  a  porcelain  mortar  and  pass  through  fine  gauze. 
Preserve  dry  in  a  well- corked  bottle. 

A  few  grains  dusted  on  the  surface  and  mixed  with  a  minute 
quantity  of  tallow  will  add  greatly  to  the  efficiency  of  the  strop. 

Another. — Equal  parts  of  opticians'  rouge  and  the  finest  washed 
flour  of  emery,  mixed  with  a  sufficient  quantity  of  vaseline  to  make 
a  stiff  paste. 


200  PRACTICAL    MICROSCOPY. 

SILVER   STAINING   SOLUTION. 

Nitrate  of  silver, 5  grains. 

Water  (distilled), 4  ounces. 

Used  for  the  demonstration  of  cement  substance  between  cell 
elements. 

OSMIC   AGID   SOLUTION. 

Osmic  acid,       .....         1  gramme. 
Water,       ......     100  cubic  cent. 

The  acid  is  found  in  market  sealed  in  glass  tubes  holding  one 
gramme  each.  The  utmost  care  should  be  taken  to  avoid  inhaling 
the  vapor  from  the  pure  acid  as  it  produces  an  intense  inflamma- 
tion of  the  respiratory  surfaces.  The  best  method  of  handling  the 
material  is  to  measure  100  c.c.  of  water,  place  it  in  a  strong  bottle, 
and  then  drop  in  the  tube  containing  the  osmic  acid.  Then  with 
u  glass  rod  break  the  tube.  The  bits  of  glass  need  not  be  removed. 
Keep  the  bottle,  tightly  stoppered,  in  a  cool  dark  place. 

Osmic  acid  is  used  in  histology  on  account  of  its  action  upon 
fatty  substances — i.e.,  staining  them  of  a  deep  brown  or  black.  ' 

WEIGERT'S   H^EMATOXYLIN    STAINING   FOR   MEDUL- 
LATED   NERVE   TISSUE. 

Formulae. 

1.  A  saturated  aqueous  solution  of  neutral  acetate  of  copper. 

2.  Strong  haematoxylin  staining  fluid,  vide  text. 

3.  Borax,  ferridcyanide  of  potassium,  aa  1  drachm. 
Water, 4  fluid  ounces. 

Process. 

1.  Allow  the  sections  to  remain  in  1  for  twenty-four  hours.* 

2.  Wash  in  clean  water  for  a  few  moments  only,  and  transfer 
to  2.     Brain  sections  will  require  from  two  to  three  days,  and 
spinal  cord  twenty-four  hours  for  complete  staining.     They  must 
appear  almost  black.     If  the  hardening  has  been  effected  with  the 
bichromate  solution  as  given  in  the  text  (vide  hardening  fluids), 
maceration  of  the  sections  in  the  cupric  acetate  may  be  omitted. 

3.  Wash  in  water  for  five  minutes  and  transfer  to  3.     They 

*  The  hsema.  solution  gives  the  best  results,  in  this  staining,  if  kept 
at  temperature  of  about  100°  F. 


KARYOKINESIS.  201 

may  be  allowed  to  remain  for  twelve  hours  without  harm.     Gen- 
erally an  hour  will  be  sufficient. 

4.  Wash  in  water. 

5.  Dehydrate  gradually,  first   placing   in   dilute   alcohol,  and 
afterward  in  stronger.     The  sections  can  now  be  kept  in  alcohol 
indefinitely.     If  the  tissue  has  been  infiltrated  with  celloidin,  the 
-sections  must  not  be  held  in  ninety-five  per  cent  alcohol  longer 
than  five  minutes,  as  the  infiltrating  medium  will  be  dissolved. 

6.  Clarify  with  oil  of  cloves — oil  of  bergamot  for  celloidin  spec- 
imens— and  mount  in  dammar. 

The  method  does  not  produce  bright  colors,  but  it  gives  a  very 
remarkable  differentiation  of  nerve  tissue,  by  staining  the  medul- 
lary substance  violet,  and  the  axis  cylinders  brown.  It  is  particu- 
larly valuable  in  pathological  histology. 

BAYBERRY   WAX    INFILTRATING  METHOD. 

In  answer  to  many  inquiries  regarding  the  material  used  in 
this  process,  I  may  say  that  Messrs.  Eimer  &  Amend,  chemists,  of 
New  York,  from  whom  my  supply  was  originally  obtained,  state 
that  the  article  furnished  me  was  the  Japan  wax.  Dr.  J.  W.  Black- 
burn, of  Washington,  D.  0.,  kindly  informs  me  that  this  is  the 
product  of  Rlius  succedanea.  The  material  with  which  I  have  had 
the  best  results  was  of  a  very  pale  yellow  or  canary  color.  The 
darker  specimens  are  unsuitable. 

KARYOKINESIS. 

The  phenomena  attending  cell-division  are  best  shown  in  the 
thin  gill-plates  or  caudal  fin  of  larvae  of  the  salamandra.  Very 
fair  demonstrations  may  be  made  from  rapidly-growing  tumors,  as 
carcinomata,  if  after  removal  they  are  sliced  thin  and  immediately 
fixed. 

Flemming's  Fixing  Fluid* 

Ohromicacid,  0.25  per  cental 

Osmic  acid,  0.1         "         >  in  water. 

Glacial  acetic  acid,  0.1         " 

Half  an  hour's  immersion  will  usually  suffice,  after  which  thie 
tissue  is  rinsed  quickly  in  water  and  transferred  to  absolute  alco- 
hol, where  it  may  remain  until  ready  to  cut.     The  parts  of  larvae, 
above  mentioned,  are  of  course  sufficiently  thin  without  sectioning. 
*  "Microtomist's  Vade-mecum,"  Lee.     London,  1885. 


202  PRACTICAL    MICROSCOPY. 

For  staining,  haema.  or  picro-carmine  answer  well,  although 
sanranin  is  preferred  by  Strassburger.  A  saturated  solution  of 
the  dye  in  absolute  alcohol  is  diluted  with  an  equal  volume  of 
water  and  allowed  to  act  on  the  tissue  for  twenty-four  hours.  Wash 
thoroughly  with  absolute  alcohol,  clear  in  oil  of  cloves,  and  mount 
in  dammar. 

The  highest  powers  are  necessary  for  successful  demonstration. 


FIXING  AND   STAINING   THE   CORPUSCULAR  ELE- 
MENTS   OF   BLOOD. 

The  following  method,  which  has  been  elaborated  by  Prof. 
Gaule,  of  Zurich,  will  prove  more  satisfactory  than  processes  which 
involve  the  drying  of  the  blood.  The  essential  steps  are : 

1.  Transferrence  to  the  slide.     This  must  be  accomplished  very 
quickly  to  provide  against  changes  in  the  corpuscular  elements, 
which  occur  soon  after  removal  from  the  vessels.     If  to  be  taken 
from  the  living  animal — and  the  frog  is  best  for  beginners — the 
surface  must  be  scrupulously  clean,  a  small  vessel  punctured  with 
the  needle,  and  a  minute  drop  of  blood  carried  to  the  surface  of  a 
slide  by  means  of  a  glass  rod.     The  blood  is  spread  in  a  thin  layer^ 
after  which,  and  before  drying,  the  elements  are  to  be  fixed. 

2.  Fixing. — A  portion,  say  fl.  5  ij.,  of  a  saturated  aqueous  solu- 
tion of  bichloride  of  mercury  having  been  prepared  in  a  saucer,  the 
blood  slide  is  submerged  in  the  liquid.     Five  minutes  suffice  for 
this  work. 

3.  Washing  is  accomplished  by  immersing,  the  slide  for  a  mo- 
ment in  a  saucer  of  distilled  water,  after  which  the  action  is  com- 
pleted by  placing  in  absolute  alcohol  for  five  minutes.     Drain  on 
bibulous  paper  for  a  moment. 

4.  Staining. — Moisten  the  blood  with  a  little  distilled  watery 
drain,  and  afterward  drop  a  few  minims  of  haema.  solution  on  the 
horizontally  placed  slide.     Ordinary  haema.  will  answer  perfectly 
if,  to  about  a  drachm  of  the  solution,  two  drops  of  alcohol  are 
added.     The  staining  is  complete  in  five  minutes.     Wash  in  dis- 
tilled water,  and  again  stain  as  before  with  a  one-per-cent  aqueous 
solution  of  nigrosin.     Again  wash  with  distilled  water,  and  again 
stain  as  before  with  eosin  one  part,  alcohol  50  parts,  distilled  water 
150  parts,  for  one  minute. 

5.  Mountin     —A  permanent  specimen  is  completed  by  washing 
the  film  of  blood  with  strong  alcohol.     A  drop  of  oil  of  cloves  gives 


FIXING    BLOOD-CORPUSCLES.  208 

translucency  in  a  moment,  after  which  it  is  drained  oft',  a  drop  of 
dammar  added,  and  the  cover  applied. 

The  nuclei  of  the  red  corpuscle  of  the  frog  take  the  blue  hsema., 
while  a  variety  of  white  corpuscles  with  a  large  round  or  spindle- 
shaped  nucleus — the  licematoblast  of  Hay  em — has  its  protoplasm 
stained  blue-black  by  the  nigrosin.  Ehrlich  has  given  the  name 
eosinopMlous  cells  to  those  white  corpuscles  with  several  nuclei 
whose  granular  protoplasm  takes  the  eosin  deeply.  Other  forms  of 
colorless  blood -corpuscles  as  amcebocytes  and  endotlielioid  cells  are 
differentiated  by  this  mode  of  fixing  and  triple  staining.  The  high- 
est powers  of  the  microscope  are  required. 


INDEX 


Abbe*  condenser,  4 
Abdominal  cavity,  162 

salivary  gland,  159 
Aberration,  chromatic,  2 
spherical,  2 

Absorption  from  intestine,  88 
Acetate  of  copper,  200 
Acid,  acetic,  31 
chromic,  22 
hydrochloric,  22 
nitric,  22 
osmic,  49 

osmic,  solution,  200 
picric,  26 
Acini,  compound,  155 

simple,  155 
Acinous  glands,  155 
Adenoid  reticulum,  167 
tissue,  61,  167 
tissue  in  thymus  body,  178 
tissue,  Klein  on,  167 
Adipose  tissue  in  bronchi,  99 
Adventitia  of  arteries,  66 
Afferent  glomerular  arterioles,  125 
Agents,  staining,  25 
Agminate  glands,  91 
Ailantus  pith,  13 
Air,  atmospheric,  100 
bubbles,  36 
sacs,  100 
vesicles,  100 

Albuminate  of  silver,  164 
Albuminous  cement,  163 
Alcohol  "  A,"  "  B,"  and  "  C,"  21 

hardening,  20 
Alum,  25 
Alveoli,  gland,  155 

pulmonary,  100 
Arnoebocytes,  203 
Ampulliform  dilatation,  97 
Aniline  colors,  198 
Anterior  commissure,  185 

median  fissure,  185 
Appendages  of  skin,  71 
Appendix,  xiphoid,  58 
Arachnoid,  191 
Arcade,  arterial,  124 


Areas,  physiological,  of  spinal  cordr 

185 

Areolar  tissue,  51 
Arrectores  pili,  74 
Arrovyroot  starch,  38 
Arterial  arcade,  124 
Arteries,  66 

adventitia  of,  66 
intima  of,  66 
large,  67 

lymphatics  of,  162 
media  of,  66 
Arteriolse  rectse,  126 
Artery,  bronchial,  95,  98 
hepatic,  107 
phrenic,  150 
pulmonary,  99 
renal,  124,  150 
splenic,  173 
typical,  66 

Articular  cartilage,  56 
Artificial  gastric  fluid,  22 
Ascending  limb  of  Henle,  123 
Asphaltum,  198 
Atmosphere,  100 
Attachment,  freezing,  16 
Auerbach's  plexus,  86,  91 
Author's  microtome,  15 
Axis  cylinder,  180 

Bacteria  in  urine,  37 
Balsam,  xylol,  197 
Basement  membrane,  99 

membrane  of  corium,  71 
Bayberry  tallow,  22,  201 
Beaker  cells,  97 
Bellini,  tubule  of,  124 
Bergamot  oil,  27 
Bichromate  of  potash,  22 
Bile  capillaries,  108 

ducts,  origin  of,  118 
Bipolar  cells,  50 

nerve  cells,  181 
Birds,  blood  of,  48 
Blackburn,  Dr.  J.  W.,  201 
Black  japan,  198 
varnish,  198 


206 


INDEX. 


Bladder  of  frog,  62 
urinary,  149 

Blood  corpuscle  as  test,  7 

corpuscle,  colorless,  49 
corpuscle,  red,  47 
corpuscles,  staining,  203 
corpuscles,  white,  49 
fixing  and  staining,  202 
of  birds,  48 
of  camelidae,  48 
of  fishes,  48 
of  invertebrates,  48 
of  reptiles,  48 
oxygenation  of,  100 
plates,  48 

supply,  hepatic,  106 
supply  of  ovary,  149 
supply  of  spleen,  173 
vessels,  66 

vessels  of  bronchi,  98 
vessels  of  epineurium,  182 
vessels  of  glands,  150 
vessels  of  kidney,  124 
vessels  of  omentum,  67 
vessels  of  pulmonarv  alveo- 
lus, 67 

vessels  of  skin,  70 
vessels  of  spinal  cord,  189 
vessels,  pulmonary,  99 

Bodies,  Malpighian,  of  kidney,  122 
Malpighian,  of  spleen,  173 

Body,  suprarenal,  120,  150 
thymus,  177 

Bone,  58  * 

corpuscles,  59 
decalcifying,  22 
mounting  of,  61 

Borax  carmine  staining  fluid,  26 

carmine  staining  process,  30 

Bowman,  capsule  of,  122 

Bowman's  muscle  discs,  65 

Brain,  191 

ganglia  of,  191 
gray  matter  of,  191 
hardening  of,  192,  200 
lymph  cavities  of,  191 
membranes  of,  191 
neuroglia  of,  182 
section  cutting  of,  192 
sulci  of,  191 
white  matter  of,  191 

Branched  tubular  glands,  154 

Bronchial  artery,  98 

glands,  96,  154 
tube,  94 
vein,  98 

Bronchi,  94 

adipose  tissue  in,  99 
basement  membrane  of, 99 
blood-vessels  of,  98 
cartilage  in,  98 
glands  of,  98 


Bronchi,  mucosa  of,  98 

muscular  coat  of,  98 
nerves  of,  98 
staining  of,  97 
subdivision  of,  94 
terminal,  97,  101 

Bronchus,  layers  of,  95 
of  pig,  44 

Brood  nests,  179 

Brownian  movement,  36 

Brunner's  glands,  89 

Bubbles,  air,  36 

Buccal  epithelium,  41 

Cable,  telegraphic,  181 
Calyces  of  kidney,  120 
Camelidse,  48 
Canal,  central,  186 
Canaliculi,  58 
Canal,  portal,  108 
Canals,  dentinal,  78,  81 

Haversian,  59 
Cancer,  epithelial,  179 
Capillaries,  66 

bile,  108 

lymphatic,  161 

of  glands,  153 

of  ovary,  149 

of   supra-renal  body, 

150 

stomata  of,  67 
tortuous,  in  lung,  103 
Capsule  of  Bowman,  122 
of  Grlisson,  106 
of  kidney,  120 
of  lymph  nodes,  167 
of  thymus  body,  177 
supra-renal,  150 
Carcinomata,  201 
Cardiac  gland-tubes,  84 

muscular  fibre,  65 
Care  of  objectives,  34 

of  the  microscope,  34 
Carmine  and  picric  acid  staining, 

31 
movement  of  particles  of, 

36 

No.  40,  26 
staining  fluid,  26 
Carpenter,  Prof.  Wesley  M.,  11 
Cartilage,  56 

articular,  56 
corpuscles,  56 
elastic,  57 
fibro,  56 
hyaline,  56 
plates  in  bronchi,  98 
reticular,  57 

Casts,  urinary,  preserving,  199 
Caudal  fin,  201 
Cavities,  lymphatic,  161 
Cavity,  abdominal,  162 


INDEX. 


207 


Cavity,  cranial,  191 
spinal,  191 
thoracic,  162 
Cell  body,  39 

cement,  163 
distribution,  40 
division,  201 
primordial,  147 
proliferation,  40,  201 
structure,  Ehrlich  on,  203 
typical,  146 
wall,  39 

Celloidin  infiltration,  23 
Cells,  beaker,  j~ 
bipolar,  50 
bipolar  nerve,  181 
border,  85 
central,  85 
chief,  85 
ciliated,  45 

ciliated  from  oyster,  45 
columnar,  41 
covering,  51 
Deiter's,  183 
€ndothelial,  51 
endothelioid,  203 
«osinophilous,  203 
epithelial,  51 
flat,  41 
ganglion,  181 
glandular,  51 
goblet,  97 
hepatic,  109 
in  urine,  143 
lining,  51 
lymphoid,  61,  161 
mucous,  97 
multinucleated    in    thyrnus 

body,  179 
mult i  polar,  50 
multipolar  nerve,  181 
nerve,  50,  181 
of  Purkinje,  194 
outlining    of,   by  silver   ni- 
trate, 164 
parietal,  85 
polar,  47,  50 
polyhedral,  49 
quadripolar  nerve,  181 
spheroidal,  47 
spider,  183 
stellate,  47,  50 
tailed,  from  pelvis  of  kidney, 

140 

teased,  hepatic,  113 
tripolar,  50 
tripolar  nerve,  181 
typical,  39 
unipolar,  50 
unipolar  nerve,  181 
uterine,  136 
vacuolated,  of  bladder,  142 


Cells,  vaginal,  136 

variation  in  form,  40 
Cement,  cell,  163 
zinc,  198 

Central  canal,  186 
Cerebellar  tracts,  direct,  185 
Cerebellum,  194 

cortex  of,  194 
folia  of,  194 
Cerebral  layers,  192 
Cerebro-spinal  system,  180 
Cerebrum,    practical    demonstra- 
tion of,  192 
staining  of,  192 
Cervix  uteri,  glands  of,  154 
Chains,  Graafian,  147 
Chamois  leather,  34 
Change,  retrograde,  20 
Channels,  lymph,  161 
spleen,  173 

Chinks,  lymphatic,  161 
Chloroform,  Squibb's,  197 
Chromatic  aberration,  2 
Chromic  acid  hardening,  21 

acid  fixing,  21 
Chyle  receptacle,  161 
Chylopoietic  viscera,  106 
Cicatricial  tissue,  146 
Ciliated  cells  from  oyster,  45 

columnar  cells,  45 
Circulation,  lymphatic,  161 
Cirrhotic  liver,  cells  from,  52 
Cleaning  cover-glasses,  31 

slides,  31 

Clefts,  lymphatic,  16: 
Clove  oil,  28 

oil,  removal  o-i,  33 
Coarse  adjustment,  1 
Coiled  tubular  glands,  154 
Collecting  tubule,  124 
Collodion,  24 
Color  in  air-bubbles,  36 
Coloring  drawings,  9 
Colorless  blood-corpuscles,  49 
Colors,  aniline,  198 

oil,  198 

Column  of  Goll,  187 
Columnar  cells,  44 
Columns,  postero-external,  185 
cortical,  120 
postero-internal,  185 
Commissure,  anterior  gray,  185 
posterior  gray,  186 
white,  185 
Compound  acini,  155 

acinous  gland,  157 
Concavity  of  blood-discs,  48 
Condenser,  4 

Abbe",  4 

Conducting  portion  of  nerves,  180 
Conductor,  electrical,  181 
Coniferous  wood,  38 


208 


INDEX. 


Connective-tissue  corpuscles,  51 
Connective  tissue  of  liver,  106 
tissue  of  lung,  99 
tissue  of  nervous  sys- 
tem, 182 

tissue  of  pancreas,  159 
tissue  of  parotid  gland, 

157 

tissues,  51 
tissues,  special,  61 
Conservation  of  vision,  7 
Constrictions  of  Ranvier,  181 
Contractile  rods,  63 
Convoluted  tubule,  122 
Cooper's  glue,  198 
Copper,  acetate,  200 

sulphate  of,  22 
Cords,  follicular,  1G7 
Cord,  spinal,  185 
Corium,  69 

basement  membrane  of,  71 
Cork  support,  19 
Corn  starch,  38 
Cornu  of  spinal  cord,  185 
Corpuscles,  blood,  203 

blood,  fixing  of,  202 
bone,  59 
cartilage,  56 
connective-tissue,  51 
HassaFs,  179 
lymph,  174 
pus,  49 

salivary,  37,  41 
tactile,  71 

Corpus  luteum,  144,  146 
Cortex  of  cerebellum,  194 
of  kidney,  120 
of  thymus  body,  178 
Cortical  columns,  120 
Corundum  hones,  1 7 
Cotton  fibres,  37 
Cover-glass,  31 
Cover-glass,  pressure  of,  36 
Covering  cells,  51 
Crossed  pyramidal  tracts,  185 
Crusta  petrosa,  80,  81 

petrosa,  lacunae  of,  80 
Crypts  of  LieberkUlm,  89 
Crystals,  fat,  55 
Cul-de-sac,  vaginal,  136 
Currents,  thermal,  36 
Cuticula,  78 
Cylinder,  axis,  180 

Dammar,  mode  of  using,  33 

varnish,  184 
Decalcificatiori.  61 

of  teeth,  22,  80 
Decalcifying  of  bone,  22 
Degeneration,  fatty,  155 
Dehydrating  tissues,  28 
Deiter's  cells,  183 


Dentinal  canals,  78,  82 
elements,  82 
fibres,  78,  82 
sheath,  82 
strite,  82 
Dentine,  78,  81 
Deposits,  urinary,  135,  143 
Derma,  69 

basement  membrane  of,  71 
Descending  limb  of  Henle,  123 
Development  of  ovum.  147 
Diameter  of  kidney  tubes,  122,  123 
Diaphragm,  central  tendon  of,  163 
Differentiation  of  cell  elements,  203. 
Disc,  HensenX  63 
Discs,  intervertebral,  57 

of  Bowman,  65 
Discus  proligerus,  146 
Dissociating  fluids,  9 

process,  22 

Distal  convoluted  tubule,  123 
Distilled  water,  163 
Distribution,  cell,  40 
Direct  cerebellar  tracts,  185 

pyramidal  tracts,  185 
Division  of  cells,  201 
Dog,  kidney  of,  127 
stomach  of,  86 
Double  staining,  29,  31 
Drainage,  tissue,  161 
Duct,  hepatic,  106 
lymph,  90 
pancreatic,  159 
papillary,  124 
Ductless  glands,  173 
Ducts,  lymphatic,  161 
mesenteric,  162 
thoracic,  162 
Dura  mater,  191 
Dust  on  lenses,  34 

Efferent  glomerular  arteriole,  125 

veins  of  lymph  nodes,  167 
Ehrlich  on  cell  elements,  203 
Elastic  cartilage,  57 

lamina  of  blood-vessels,  66 
tissue,  52 

tissue  in  bronchi,  98 
Elder  pith,  13 
Electrical  conductor,  181 
Elements,  dentinal,  82 

of  ganglia,  181 
sarcous,  65 
structural,  35 
structural,    of   nervous. 

system,  180 
Embryonic  tissue,  62 
Emery,  flour  of,  199 
Enamel  of  teeth,  79 
prisms,  79 
Endomysium,  64 
Endoneurium,  182 


INDEX. 


209 


Endothelial  cells,  51 
Endothelioid  cells,  203 
Endothelium,  44 

of  blood-vessels,  06 
Eosin  solution,  26 

staining,  203 
Eosinophilous  cells,  203 
E.  P.  E.  N.  formula,  182 
Epidermis,  68 
Epineuriuni,  182 

lymph-spaces  of,  182 
vessels  of,  182 
Epithelia,  glandular,  50 
Epithelial  cancer,  179 

cells,  51 
Epithelium,  buccal,  41 

of  bladder,  142 
of  ovary,  148 
of  tongue,  41 
pavement,  42 
proliferation  of,  135 
stratified,  41 
squamous,  41 
tessellated,  42 
transitional,  41 
uterine,  136 
vaginal,  136 
Ether  freezing,  16 
Eustachian  tube,  58 
Extraneous  substances,  37 

substances,  mounting 

of,  38 

Eye-lens,  3 
Eye-piece,  1 

Fasciculi,  primitive,  64 
Fat-columns  of  Satterthwaite,  70 
Fat-crystals,  55 
Fat-globules  in  milk,  35 

in     suprarenal    cap- 
sule, 152 
Fat-tissue,  54 
Fatty  degeneration,  155 
Fauces,  158 
Feathers,  38 

Fenestrated  membrane,  66 
Fermentation  spores,  38 
Ferrein,  pyramids 'of,  122,  124 
Fibres,  cotton,  37 

dentinal,  78,  82 

linen,  37 

nerve,  180 

perforating,  59 

silk,  37 

wool,  37 
Fibroblasts,  51 
Fibro-cartilage,  56 
Fibrous  tissue,  51 
Field  lens,  3 

of  view,  5 
Fin,  caudal,  201 
Fine  adjustment,  1 
14 


Fishes,  blood  of,  48 
Fissure,  anterior  median,  185 
posterior  median,  185 
transverse,  of  liver,  106 
Fixing  blood  elements,  202 
chromic  acid,  21 
fluid,  Flemming's,  201 
Flat  cells,  41  . 
Flour  of  emery,  199 
Fluid,  artificial  gastric,  22 
dissociating,  9 
Flemming's  fixing,  201 
lymphatic,  161 
preservative,  199 
Focal  adjustment,  5 
Focussing,  1,  5 
Foetal  life,  147 
lung,  103 
ovary,  148 
teeth,  80 
Folia  of  cerebellum,  194 

of  suprarenal  bodies,  150 
Follicle  of  hair,  71 
Follicles  of  Lieberkiihn,  91 
solitary,  90 
of  thymus  body,  177 
Follicular  cords,  167 
Foramen  dentium,  78 
Form  of  objects,  35 
Formulae,  miscellaneous,  197 
Fourth  ventricle,  186 
Freezing  attachment,  16 
Fresh  tissue,  20 
Frog,  bladder  of,  62 
Frog's  mesentery,  42 
Funiculus  cuneatus  of  spinal  cord, 

187 

gracilis  of  spinal  cord, 
187     . 

Gage,     Professor,     on     Japanese 

paper,  31 
Gall-duct,  107 
Ganglia,  nerve,  181 

of  brain,  191 
Ganglion  cells,  181 

cells,  poles  of,  181 
elements  of  a,  181 
Gastric  fluid,  artificial,  22 
juice,  83 
tubules,  83 
Gaule,  "Professor,  202 
Gelatinous  substance,  185 
Genitp-urinary  tract,  135 
Germinal  spot,  146 

vesicle,  146 
Gill  plates,  201 
Gland  alveoli,  155 

mammary,  155 
parotid,  156 
sebaceous,  73 
serous,  159 


210 


INDEX. 


Gland  sublingual,  157 

subrnaxillary,  158,  160 
sudoriferous,  71 
thymus,  177 
Glands,  153 

acinous,  155 
agminate,  91 
branched  tubular,  154 
bronchial,  96,  154 
Brunner's,  89 
buccal,  157 
coiled  tubular,  154 
ductless,  173 
essentials  of,  153 
gastric,  154 
intestinal,  154 
mucous,  158 
mucous  of  bronchi,  98 
of  cervix  uteri,  154 
parenchyma  of,  153 
peptic,  83 
Peyer's,  154 
pyloric,  84 
salivary,  153,  157 
sebaceous,  155 
sudoriferous,  154 
uterine,  154 
vessels  of,  153 
Glandular  cells,  50 

epithelia,  50 
structures,  staining  of, 

159 

Glassy  membrane  of  hair,  71 
Glisson's  capsule,  106 
Globules,  oil,  36 
•Glomerulus  of  kidney,  125 
Glue,  Cooper's,  198 

Le  Page's,  198 
Glycerin  iri  honing,  17 

in  mounting,  128 
Goll,  column  of,  187 
Goose-flesh,  74 
Graafian  chains,  147 

follicles,  144 
Granules,  pigment,  152 
Gray  commissure,  185 

matter  of  brain,  191 
nerve  matter,  181 
Gum,  dammar,  197 
mastic,  197 

Hsematoblast,  202 
Hsematoxylin,  25 

and  eosin,  29 
staining  fluid,  25 
staining  process,  27 
Weigert's,  200 
Hair,  37,  71 

cortex  of,  91 
follicle,  71 

follicle,  muscle  of,  74 
glassy  membrane  of,  71 


Hair,  from  shaving,  74 
inedullated,  71 
permanent  mounting  of,  74 
root-sheath  of,  71 
transverse  section  of,  71 
Hardening,  alcohol,  20 

bayberry  tallow,  22 
by  freezing,  24 
chromic  acid,  21 
of  bladder,  135 
of  brain,  192 
of  foetal  ovary,  147 
of   genito-urinary  or- 
gans, 135 
of  kidney,  127 
of  liver,  110,  113 
of  tissues,  20 
of  nerve  fibre,  180 
of  os  uteri,  135 
of  ovary,  144 
of  pancreas,  159 
of  parotid  gland,  159 
of  small  intestine,  92 
of  spinal  cord,  186 
of  spleen,  174 
of  sub  maxillary  gland, 

159 
of  suprarenal  capsule, 

150 

of  thymus  body,  177 
of  ureters,  135 
of  uterus,  135 
quick,  21 

with  Miiller's  fluid,  22 
Hartnack  objectives,  4 
Hassal's  corpuscles,  179 
Haversian  canals,  59 
system,  59 

Hayem's  hsematoblast,  202 
Heitzmann,  Dr.  Carl,  61 

on     development     of 

teeth,  80 
Henle,  loop  of,  123 

tubule  of,  123 
Hensen's  middle  disc,  63 
Hepatic  artery,  107 

blood-supply,  106 
cells,  109 
cells,  teased,  113 
duct,  106 
lobules,  106 
veins,  106 

Hilum  of  kidney,  120 
Hone,  17 

water  of  Ayr,  17 
Horns  of  ganglion  cells,  181 
Horny  layer  of  skin,  68 
Hyaline  cartilage,  55 
Hydrocarbons,  88 
Hydrochloric  acid,  22 

Ileum,  section  of,  92 


INDEX. 


211 


Illumination,  4 

Imbedding  with  ailantus  pith,  13 

with  paraffin,  13 
Incremental  lines,  79 
Infiltrating  with  bayberry  tallow, 

22 

Infiltration  with  celloidin,  23 
Infundibula  of  kidney,  120 

pulmonary,  101 
Injection  of  lung,  101 
Insects,  38 

Intima  of  arteries,  66 
Interglobular  spaces,  78,  82 
Interlobular  septa  of  lung,  100 
veins,  106 

vessels  of  kidney,  124 
Internal  elastic  lamina,  66 
Intervertebral  discs,  57 
Intestinal  lymphatics,  90 

villi,  88 
Intestine,  coats  of,  88 

of  rabbit,  45,  92 

small,  88 

Invertebrates,  blood  of,  48 
Involuntary  muscle,  63 

Japan,  black,  198 

wax,  201 

Japanese  paper,  31,  34 
Juice,  gastric,  83 

Karyokinesis,  201 

Kidney,  120 

afferent  vessels  of,  129 
arterial  arcade  of,  129 
blood-vessels  of,  124 
boundary  region  of,  144 
Bowman's  capsule  of,  129 
calyces  of,  120 
capsule  of,  120,  129 
collecting  tubes  of,  132 
convoluted  tubes  of,  129 
cortex  of,  120 
cortical  labyrinths  of,  129 
diagram  of,  121 
efferent  vessels  of,  129 
Ferrein's  pyramids  of,  129 
glomerulus*  of ,  130 
hardening  of,  127 
Henle's  limb,  130 
Henle's  loop  of,  130 
hi  him  of,  120 
infundibula  of,  120 
interlobular  blood-vessels 
.  of,  129 
intertubular  capillaries  of, 

144 

labyrinths  of,  129 
lymphatics  of,  120 
Malpighian  bodies  of,  129 
Malpighian  pyramids,  129 
markings,  129 


Kidney,  medullary  portion  of,  133 
medullary  radii  of,  129 
papillary  ducts  of,  134 
pelvis  of,  120,  140 
principal  tubes  of,  134 
scheme  of,  121 
spiral  tubes  of,  132 
tubes,  122 

tubules,  diagram  of,  123 
tubules  of,  154 

Klein  on  adenoid  tissue,  167 
on  neuroglia,  195 

Knives,  sharpening,  16 

Krause's  line,  63 

Labels  for  slides,  34 
Laboratory  microscope,  2 
microtome,  15 
Labyrinth,  kidney,  122 
Lacteals,  90 
Lacunae,  58 

of  crusta  petrosa,  80 
Lamellae,  bone,  59 
Lamina,  internal  elastic,  66 
Laminae  of  crusta  petrosa,  80 
Larvae  of  salamander,  201 
Lateral  tracts,  185 
Layers  of  cerebrum,  192 
of  epidermis,  68 
Lenses,  cleaning  soiled,  34 

water,  36 

Le  Page's  glue,  198 
Leucocythaemia,  spleen  in,  176 
Lieberkilhn,  crypts  of,  89 
Life,  foetal,  147 
Lifting  sections,  27 
Ligamentum  nuchae,  53        -  . 
Light,  transmitted,  10 
Limb  of  Henle,  123 
Limiting  membrane,  39 
Line,  Krause's,  63 

Purkinje's,  82 
Linen  fibres,  37 

for  optical  surfaces,  34 
Lines,  incremental,  79 

of  Retzius,  80 
Lining  cells,  51 

of  stomach,  83 
Links,  Graafian,  147 
Liquor  potassae,  26 
Liver,  105 

connective  tissue  of,  106 

lobules  of,  106 

of  pig,  116 

parenchyma,  108,  116 

physiological  scheme,  109 

practical  demonstration,  109 

scheme  of  structure,  106 
Lobes  of  thymus  body,  177 
Lobular    parenchyma    of     liver, 

108 
Lobule,  primary,  100 


212 


INDEX. 


Lobules,  hepatic,  106 

of  thynius  body,  177 
Loop  of  Henle,  123 
Lung,  94 

connective  tissue  of,  99 
foetal,  103 
hardening  of,  103 
injected,  102 
interlobular  septa,  100 
of  pig,  103 
parenchyma  of,  100 
staining  of,  103 
vascular  supply  of,  100 
Lymph,  161 

cavities  of  brain,  191 
ducts  of  intestine,  90 
node,  diagram  of,  168 
node,     practical     demon- 
stration of,  169 
nodes,  91,  167 
nodes,  capsule  of,  167 
nodes,  sectioning,  169 
nodes,  staining,  169 
nodes,  trabeculae  of,  167 
nodes,  vascular  system  of, 

167 

paths,  164 
paths,  valves  of,  164 
spaces  in  portal  canals,  116 
spaces  of  nerves,  182 
spaces  of  perineurium,  182 
spaces  of  spinal  cord,  190 
spaces  of  thy mus  body,  178 
Lymphatic  capillaries,  161 
ducts,  161 
system,  161 

Lymphatics  of  intestine,  90 
of  kidney,  120 
peri  vascular,  162,  190 
Lymphoid  cells,  61,  161 

Magnification  of  movements,  36 
Magnifying  power,  7 
Malpighian  bodies  of  spleen,  173 
Malpighii,  pyramids  of,  120 
Mammary  gland,  155 
Markings,  kidney,  129 
Mastic,  197 

Measurement  of  objects,  7 
Media  of  arteries,  66 
Medico-legal  work,  103 
Medulla,  186 

of  hair,  71 

of  thymus  body,  178 
Medullated  nerves,  180 
Meisser's  plexus,  91 
Membrana  granulosa,  146 

propria  of  kidney  tube, 

Membrane,  basement,  99 

basement  of  corium,71 
fenestrated,  66 


Membrane,  glassy,  71 
Limiting,  39 
peridental,  81 
tubular,  181 

Membranes  of  brain,  191 
Menopause,  144 
Merck's  hflematoxylin,  25 
Mesenteric  ducts,  25 
Mesentery,  silvered,  42 
Method  in  observation,  6 

Weigert's,  186 
Micrometers,  8 
Microscope,  1 

adjustment,  4 
care  of,  34 
sketching  from,  8 
Microtome,  laboratory,  15 
Schrauer,  14 
Stirling,  12 
the  author's,  15 
Milk,  fat-globules  in,  35 
Mirrors,  4,  5 

Miscellaneous  formulae,  197 
Molecular  movement,  37 
Mordants,  30 
Morphology,  Dr.  C.  Heitzrnann's, 

80 
Mounting  objects,  31 

extraneous   substances, 

38 

varnish,  197 
Mounts,  rings  on,  34 
Movement,  Brownian,  36 
molecular,  37 
vital,  37 

Movements,  magnification  of,  36 
Mucosa  of  bronchi,  98 

of  pelvis  of  kidney,  140 
of  small  intestine,  88 
of  stomach,  83 
of  ureter,  141 
of  uterus,  136 
of  vagina,  136 
Mucous  glands,  158 

glands  of  bronchi,  98 
Mliller,  capsule  of,  122 
Miiller's  fluid,  22 

fluid,  hardening  with,  22 
Multinucleated    cells    of   thymus 

body,  179 

Multipolar  nerve  cells,  181 
Muscle,  62 

cardiac,  65 
from  tongue,  65 
non-striated,  62 
of  hair-follicle,  74 
striated,  63 

Muscular  coat  of  bronchi,  98 
Muscularis  mucosse  of  stomach,  83 

Nerve  cells,  50,  181 

cells,  bipolar,  etc.,  181 


IXDEX. 


213 


Nerve  functioning,  181 
ganglia,  181 
spinal,  185 

staining,  Weigert's,  200 
•  trunks,    connective    tissue 

of,  181 
Nerves,  conducting  portion  of,  180 

of  special  sense,  181 
Network,  mtracellular,  in  hepatic 

cells,  117 
Neurilemma,  180 
Neuroglia,  01,  181,  186 

Klein  on,  194 
Nigrosin,  203 

Nitrate  of  silver  solution,  26 
Nodes,  lymph,  167 

of  Ranvier,  181 
Non-medullated  nerves,  181 
Non-striated  muscle,  62 
Normal  salt-solution,  180,  199 
Nuclei  of  cells,  39 
Nucleoli  of  cells,  39 

Objectives,  1 

Objects,  form  of,  35 

movement  of,  36 

Odontoblasts,  78,  81 

Oil-colors,  198 

Oil-globules,  36 

Oil  of  bergamot,  27 
of  cloves,  28 

Omentum,  55 

vessels  from,  67 

Optical  axis,  5 

Optician's  rouge,  199 

Organisms  in  urine,  37 

Organs,  urinary,  135 

Origin  of  bile-ducts,  118 

Osmic  acid,  49 

acid  solution,  200 

Osier,  Professor,  58 

Os  uteri,  136 

Ova,  146 

Ovary,  144 

blood-supply  of,  149 
corpus  luteum  of,  144 
Graafian  follicles  of,  144 
practical    demonstration, 
144 

Ovum,  development  of,  147 

Ox,  spinal  cord  of,  186 

Oxygenatipn  of  blood,  100 

Oyster,  ciliated  cells  from,  45 

Pancreas,  153 

practical  demonstration 

of,  159 

Paper,  Japanese,  Prof.  Gage  on,  34 
Papillary  ducts,  124 

eminence,  120 
Paraffin  cement,  11 

imbedding:,  13 


Parraffin  soldering,  18 
Parenchyma,  51 

of  glands,  153 
of  liver,  108,  116 
of  lung,  100 
Parotid  gland,  156 

gland,  parenchyma  of,  159 
practical     demonstration 

of,  159 

Paste,  razor-strop,  199 
Pa,tch,  Peyer's,  91 
Pavement  epithelium,  42 
Pelvis  of  kidney.  140 
Pepsin,  22 
Peptic  glands,  83 
Perforating  fibres  of  Sharpey,  59 
Perichondrium,  96 
Peridental  membrane,  81 
Perimysium,  64 

Perineurium,  lymph-spaces  of,  182 
Periosteum,  59 
Peripheral  nerve  termini,  183 
Peritoneum,  162 

of  stomach  and  intes- 
tines, 83 

Perivascular  lymphatics,  162,  190 
lymph-spaces  of  cere- 
brum, 193 
Peyer's  patch,  91 
Phrenic  artery,  150 
Pia  mater,  191 
Picric  acid  solution,  26 
Pig,  bronchus  of,  45 
kidney  of,  127 
liver  of,  116 
spinal  cord  of,  186 
Pig's  lung,  113 

Pigment  in  suprarenal  capsule,  152 
Plates,  blood,  48 

cartilage,  98 
Pleura,  100,  162 
Plexus,  Auerbach's,  86,  91 

Meissner's,  91 

Pencilling  of  serous  surfaces,  162 
Polar  cells,  47,  50 
Poles  of  ganglion  cells,  181 
Pollen,  39 
Polyhedral  cells,  49 
Portal  canal,  108 
vein,  106 

Posterior  commissure,  185 
Postero-external  columns,  185 
Postero-internal  columns,  185 
Potassium  ferridcyanide,  200 
Potato  starch,  38 
Power,  magnifying,  7 
Practical    demonstration.      Bron- 
chus of  pig,  97 
demonstration.       Cere- 
bellum, 196 

demonstration.       Cere- 
brum, 192 


214 


INDEX. 


Practical    demonstration.    Devel- 
opment of  ovary,  147 
demonstration.  Human 

liver,  113 
demonstration.  Human 

lung,  105 

demonstration.      Intes- 
tine, 92 
demonstration.  Kidney, 

140 
demonstration.      Liver 

of  pig,  109 

demonstration.      Lym- 
phatics of  central  ten- 
don of  diaphragm,  168 
demonstration.    Mesen- 
teric  lymph  node,  169 
demonstration.    Ovary, 

144 
demonstration .     P  a  n  - 

creas,  159 

demonstration.     Parot- 
id gland,  159 
demonstration.    Spinal 

cord,  186 
demonstration.  Spleen, 

173 
demonstration.     Stoii-- 

ach,  87 
demonstration-     Sub- 

maxillary  gland,  159 
demonstration.    Supra- 
renal capsule,  150 
demonstration.    Teeth, 

81 
demonstration.     T  h  y  - 

mus  body,  177 
demonstration.         Uri- 
nary bladder,  141 
demonstration.  Ureter, 

140 
demonstration.  Uterus, 

138 
demonstration.  Vagina, 

138 

Preservative  fluid,  199 
Pressure  of  cover,  36 
Prickle  cells  of  skin,  69 
Primitive  fasciculi,  64 
Primordial  cell,  147 
Prismatic  color  in  air-bubbles,  36 
Prisms,  enamel,  79 
Process,  decalcifying,  22 
dissociating,  22 
Processes  of  odontoblasts,  82 
Proliferation,  cell,  40,  201 
Protoplasm,  89 

Proximal  convoluted  tubule,  122 
Pulmonary  alveoli,  100 
artery,  99 
infundibula,  101 
Pulp  of  teeth,  78 


Pulp  of  spleen,  173 
Purkinje,  cells  of,  194 

granular  layer  of,  79 
Purkinje's  line,  82 
Pus-corpuscles,  49 
Pyloric  glands,  84 
Pyramidal  tracts,  185 
Pyramids  of  Ferrein,  122 

of  Malpighii,  120 

Quadripolar  nerve  cells,  181 
Quick  hardening,  20 

Rabbit,  central  diaphragmatic  ten- 
don of,  163 
intestine.  45,  92 
kidney  of,  127 
spinal  cord  of,  187 

Ranvier's  nodes,  181 

Rapid  hardening,  21 

Razor  stropping,  18 

strop  paste,  199 

Receptaculum  chyli,  91,  161 

Red  blood-corpuscle,  47 
muscle,  63 

Renal  artery,  124,  150 

Reptiles,  blood  of,  48 

Reservoir,  lymph,  161 

Rete  Malpighii  of  skin,  69 
mucosum  of  skin,  69 

Reticular  cartilage,  57 

Reticulum,  40 

adenoid,  167 

Retrograde  changes,  20 

Retzius,  lines  of,  80 

Ringing  mounts,  34,  198 

Rods,  contractile,  63 

Rogers'  stage  micrometer,  8 

Root-sheath  of  hair,  71 

Rouge,  optician's,  199 

Sacs,  air,  100 

Salamander,  201 

Salivary  abdominal  gland,  154 
corpuscles,  37,  41 
glands,  157 

Salt  solution,  normal,  199 

Salter,  incremental  lines  of,  79 

Sarcolemma,  63 

Sarcous  elements,  65 

Satterthwaite,  fat-coluinns  of,  70 

Scalp,  hair  from,  74 

Schrauer  microtome,  14 

Schwann,  white  substance  of,  180 

Sebaceous  gland,  74,  155 

Sebum,  74 

Secretion  of  succus  entericus,  88 
pancreatic,  159 

Section  cutting,  9 

cutting,  free-hand,  10 
cutting,  with  Stirling  mi- 
crotome, 12 


INDEX. 


215 


Section  lifter,  32 
needle,  27 
spoon, 32 

Sediments,  urinary,  199 
Septa,  interlobular,  of  lung,  100 
Septum  narium,  56 
Serous  gland,  159 

surfaces,  pencilling  of,  163 
Sharpening  knives,  16 
Sharpey's  fibres,  59 
Sheath,  dentinal,  78 
Sheep,  spinal  cord  of,  187 
Shellac  varnish,  198 
Silk  fibres,  37 
Silver,  albuminate  of,  164 
nitrate  of,  26 
solution,  26 
staining  solution,  200 
Silvered  mesentery,  42 
Skeletal  muscle,  63 
Setching  from  microscope,  8 
Skin,  68 

chamois,  34 

practical  demonstration,  74 
staining  of,  74 
sudoriferous  glands  of,  72 
Slides,  labelling,  34 
Small  intestine,  88 
Smooth  muscle,  62 
Soda,  acetate  of,  199 
Soldering  with  paraffin,  18 
Solitary  "glands,"  91 

lymphatics,  88 
Solution,  chromic-acid,  22 
eosin,  26 
normal  salt,  180 
osmic-acid,  200 
picric-acid,  26 
silver,  26,  200 
Space,  subarachnoid,  191 

subdural,  191 
Spaces,  interglobular,  78,  82 

venous,  173 

Special  connective  tissues,  61 
sense,  nerves  of,  181 
Specimen,  permanent,  33 

trays,  34 

Spheroidal  cells,  47 
Spider  cells,  183 
Spinal  cord,  185 

cord,     central     canal     of, 

186 

cord,  commissures  of,  185 
cord,  diagram  of,  185 
cord,  f uniculus  cuneatus  of, 

187 
cord,  f  uniculus  gracilis  of, 

187 

cord,  lymph-spaces  of,  190 
cord,  nerve  roots  of,  185 
cord  of  domestic  animals, 
187 


Spinal  cord,  practical  demonstra- 
tion, 186 
cord,  physiological  areas  of, 

185 
cord,  substantia  gelatinosa 

of,  185 
nerve,  185 
Spiral  tubule,  122 
Spirals  from  tea  leaf,  38 
Spleen,  173 

Malpighian  bodies  of,  173 
practical     demonstration 

of,  173 
pulp,  173 

supernumerary,  174 
Spoon,  section,  32 
Spores,  fermentation,  38 

vegetable,  38 
Spot,  germinal,  146 
Squamous  epithelium,  41 
Squibb's  chloroform,  197 
Stage  micrometer,  8 
Staining  agents,  25 

carmine  and  picric  acid. 

31 

double,  21,  29 
eosin,  203 

fluid,  borax-carmine,  26 
fluid,  hsema.,  25 
fresh  tissue,  25 
hsema.,  27 

hsema.  and  eosin,  27 
nigrosin,  203 
osmic  acid  in  nerve  tissue, 

180,  200 
silver,  163 
solution,  silver,  200 
Weigert's  nerve,  200 
Starch,  38 

Stars  of  Verheyen,  126 
Stellate  cells,  47,  50 

sternum,  163 
Stirling  microtome,  12 
Stirling's  processes,  22 
Stomach,  83 

and  intestines,  83 
hardening  of,  87 
of  dog,  86 

Stoniata,  44,  67,  164 
Straight  kidney  tubule,  124 
Stratified  epithelium,  41 
Stratum  corrieum  of  skin,  68 

granulosum  of  skin,  68 
lucidum  of  skin,  68 
Striae,  dentinal,  82 
Striated  muscle,  63 
Stroma  of  ovary,  144 
Stropping  knives,  18 
Structural  elements,  35 
Structure,  glandular,  157 
Subarachnoid  space,  191 
Subcutaneous  cellular  tissue,  70 


216 


1XDKX. 


Subdural  space,  191 
Sublingual  gland,  157 
Sublobular  veins,  100 
Submaxillary  gland,  158 
Substance,  white,  of  Schwann,  180 
Substances,  extraneous,  87 
Substantia  gelatinosa,  185 
Succus  entericus,  88 
Sudoriferous  gland,  73,  154 
Sulci,  191 

Sulphate  of  copper,  22 
Supernumerary  spleen,  174 
Suprarenal  bodies,  120 
capsule,  150 
capsule,  practical  de- 
monstration of,  150 
Sweat-glands,  number  of,  74 
Sweat -tubes.  154 
Sympathetic  system,  181 
System,  cerebro-spinal,  180 

Haversian,  59 

lymphatic,  161 

sympathetic  nervous,  181 

the  nervous,  180 

vascular,  of  kidney,  125 

Tactile  corpuscles,  71 

Tailed  cells  from  ureter  and  pelvis 

of  kidney,  140 
Tallow,  bayberry,  22 
Tea  leaf,  38 

Teased  nerve  fibres,  180 
Teasing,  9 

glandular  structures,  159 
Teeth,  78 

decalcification  of,  80 
development  of,  80 
foetal,  80 

grinding  sections  of,  80 
practical  demonstration  of, 

80 

Telegraphic  cable,  181 
Tendon,  51 

diaphragmatic,  163 
Terminal  bronchi,  97,  101 
Termini,  nerve,  181 
Tesselated  epithelium,  42 
Thermal  currents,  36 
Thoracic  cavity,  162 

duct,  162 

Thymus  body,  hardening  of,  177 
body,  Hassal's  corpuscles 

in,  179 

Tissue,  adenoid,  61,  167 
adipose,  54 

adipose  in  bronchi,  99 
areolar,  51 
cicatricial,  146 
connective,  51 
connective,      of      nerve 

trunks,  181 
drainage,  161 


Tissue,  embryonic,  62 
fat,  54 
fibrous,  51 
fresh,  20 
hardening  of,  20 
muscular,  62 

sustentacular  of  brain,  183 
white  fibrous,  51 
yellow  elastic,  52 
Tissues,  dehydration  of,  28 

selective  power  of,  25 
special  connective,  61 
traiislucency  of,  28 
Tongue,  158 

epithelium  of,  41 
Tooth,  canine,  81 
Tortuosity  of  hepatic  cell-columns, 

115 
Trabeculse  of  lymph  nodes,  167 

splenic,  173 
Trachea,  56,  158 
Tract,  crossed  pyramidal,  183 

genito-urinary,  135 
Tracts,  direct  cerebellar,  185 
direct  pyramidal,  185 
lateral,  185 

Transitional  epithelium,  41 
Transmitted  light,  9 
Transverse  fissure  of  liver,  106 
Trigone,  142 
Tripolar  cells,  50 

nerve  cells,  181 
True  skin,  69 
Tube,  bronchial,  94 

Eustachian,  58 
Tubular  glands,  153 

membrane,  181 
Tubule,  Bellini's,  124 
collecting,  124 
gastric,  83 
Henle's,  123 

proximal  convoluted,  122 
spiral,  122 
straight,  123 

Tubules,  uriniferous,  121 
Tumors,  201 

Tunica  albuginea,  144,  147 
Turpentine,  197 
Typical  artery,  66 
cell,  39,  146 

Unipolar  cells,  50 

nerve  cells,  181 
Ureter,  120 

muco«a  of,  141 

Urinary  casts,  preserving,  199 
deposits,  135 
organs,  135 
Urine,  bacteria  in,  37 
cells  in,  143 

course  of,  in  kidney,  122, 
126,  127 


1X1)  EX. 


217 


TJriniferous  tubules,  122 
Uterus,  mucosa  of,  136 

Vaeuolated  cells,  vaginal,  136 
Vagina,  cul-de-sac  of,  136 

inucosa  of,  136 
Valves  of  lymph  paths,  164 
Variation  of  cell  forms,  40 
Varicosities  of  nerves,  181 
Varnish,  asphaltum,  198 
black,  198 
dammar,  197 
shellac,  198 
Vascular  supply  of  lung,  100 

supply  of  lymph  nodes, 

167 

system  of  spleen,  173 
system  of  thymus  body, 

179 

Vegetable  spores,  38 
Vein,  bronchial,  98 

portal,  106 
Veins,  66 

central,  106 

efferent,  of  lymph  nodes,  167 
hepatic,  106 
interlobular,  106 
intralobular,  106 
sublobular,  106 
Venous  spaces  of  spleen,  173 
Venulae  rect<e.  ]  26 
Venules,  66 
Verheyen,  stars  of,  126 


Vesicle,  germinal,  146 
Vesicles,  air,  100 
A7i Hi  of  intestine,  88 
Viscera,  chylopoietic,  106 
Vital  movements,  37 
Voluntary  muscle,  63 

Wall,  cell,  39 

uterine,  136 

Walls  of  stomach  and  intestines,  83 
Water,  boiled,  163 

distilled,  163 

lenses,  36 

of  Ayr  hone,  17 
Wax,  bayberry,  22,  201 
Weigert's  nerve-staining,  186,  200 
Wood,  coniferous,  38 
Wenham  objective,  2 
Wheat  starch,  38 
White  blood-corpuscles,  49 

commissure,  185 

fibrous  tissue,  51 

matter  of  brain,  191 

substance  of  Schwann,  180 

Xiphoid  appendix,  58 
Xylol,  balsam,  197 

Yellow  elastic  tissue,  52 

Zinc  cement,  198 
Zona  pellucida,  146 
vasculosa,  144 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

6NNJNSV  UWH 

This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 


AUG  15  1963 

2r  m  r,fen\/  \, 

I  Ala  00  A 

LD  21-50m-6,'59 
(A2845slO)476 

General  Library 
University  of  California 
Berkeley 

M 


THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


